Merge pull request #8125 from eugenp/revert-8119-BAEL-3275-2

Revert "BAEL-3275: Using blocking queue for pub-sub"

core-java-modules/core-java-networking/.gitignore

@@ -0,0 +1,25 @@
+*.class
+
+0.*
+
+#folders#
+/target
+/neoDb*
+/data
+/src/main/webapp/WEB-INF/classes
+*/META-INF/*
+.resourceCache
+
+# Packaged files #
+*.jar
+*.war
+*.ear
+
+# Files generated by integration tests
+backup-pom.xml
+/bin/
+/temp
+
+#IntelliJ specific
+.idea/
+*.iml

core-java-modules/core-java-networking/README.md

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+## Core Java Networking
+
+This module contains articles about networking in Java
+
+### Relevant Articles
+
+- [Connecting Through Proxy Servers in Core Java](https://www.baeldung.com/java-connect-via-proxy-server)
+- [Broadcasting and Multicasting in Java](http://www.baeldung.com/java-broadcast-multicast)
+- [A Guide To UDP In Java](http://www.baeldung.com/udp-in-java)
+- [A Guide To HTTP Cookies In Java](http://www.baeldung.com/cookies-java)
+- [A Guide to the Java URL](http://www.baeldung.com/java-url)
+- [Working with Network Interfaces in Java](http://www.baeldung.com/java-network-interfaces)
+- [A Guide to Java Sockets](http://www.baeldung.com/a-guide-to-java-sockets)
+- [Guide to Java URL Encoding/Decoding](http://www.baeldung.com/java-url-encoding-decoding)
+- [Difference between URL and URI](http://www.baeldung.com/java-url-vs-uri)
+- [Read an InputStream using the Java Server Socket](https://www.baeldung.com/java-inputstream-server-socket)
+- [[More -->]](/core-java-modules/core-java-networking-2)

core-java-modules/core-java-networking/pom.xml

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+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>core-java-networking</artifactId>
+    <version>0.1.0-SNAPSHOT</version>
+    <name>core-java-networking</name>
+    <packaging>jar</packaging>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-java</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../../parent-java</relativePath>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-web</artifactId>
+            <version>${springframework.spring-web.version}</version>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <finalName>core-java-networking</finalName>
+    </build>
+
+    <properties>
+        <springframework.spring-web.version>4.3.4.RELEASE</springframework.spring-web.version>
+    </properties>	
+</project>

core-java-modules/core-java-networking/src/main/java/com/baeldung/networking/cookies/PersistentCookieStore.java

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+package com.baeldung.networking.cookies;
+
+import java.net.*;
+import java.util.List;
+
+public class PersistentCookieStore implements CookieStore, Runnable {
+    CookieStore store;
+
+    public PersistentCookieStore() {
+        store = new CookieManager().getCookieStore();
+        // deserialize cookies into store
+        Runtime.getRuntime()
+            .addShutdownHook(new Thread(this));
+    }
+
+    @Override
+    public void run() {
+        // serialize cookies to persistent storage
+    }
+
+    @Override
+    public void add(URI uri, HttpCookie cookie) {
+        store.add(uri, cookie);
+
+    }
+
+    @Override
+    public List<HttpCookie> get(URI uri) {
+        // TODO Auto-generated method stub
+        return null;
+    }
+
+    @Override
+    public List<HttpCookie> getCookies() {
+        // TODO Auto-generated method stub
+        return null;
+    }
+
+    @Override
+    public List<URI> getURIs() {
+        // TODO Auto-generated method stub
+        return null;
+    }
+
+    @Override
+    public boolean remove(URI uri, HttpCookie cookie) {
+        // TODO Auto-generated method stub
+        return false;
+    }
+
+    @Override
+    public boolean removeAll() {
+        // TODO Auto-generated method stub
+        return false;
+    }
+
+}

core-java-modules/core-java-networking/src/main/java/com/baeldung/networking/cookies/ProxyAcceptCookiePolicy.java

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+package com.baeldung.networking.cookies;
+
+import java.net.*;
+
+public class ProxyAcceptCookiePolicy implements CookiePolicy {
+    String acceptedProxy;
+
+    public ProxyAcceptCookiePolicy(String acceptedProxy) {
+        this.acceptedProxy = acceptedProxy;
+    }
+
+    public boolean shouldAccept(URI uri, HttpCookie cookie) {
+        String host;
+        try {
+            host = InetAddress.getByName(uri.getHost()).getCanonicalHostName();
+        } catch (UnknownHostException e) {
+            host = uri.getHost();
+        }
+
+        if (HttpCookie.domainMatches(acceptedProxy, host)) {
+            return true;
+        }
+
+        return CookiePolicy.ACCEPT_ORIGINAL_SERVER.shouldAccept(uri, cookie);
+    }
+}

core-java-modules/core-java-networking/src/main/java/com/baeldung/networking/proxies/CommandLineProxyDemo.java

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+package com.baeldung.networking.proxies;
+
+import java.net.URL;
+import java.net.URLConnection;
+
+public class CommandLineProxyDemo {
+
+    public static final String RESOURCE_URL = "http://www.google.com";
+
+    public static void main(String[] args) throws Exception {
+
+        URL url = new URL(RESOURCE_URL);
+        URLConnection con = url.openConnection();
+        System.out.println(UrlConnectionUtils.contentAsString(con));
+    }
+
+}

core-java-modules/core-java-networking/src/main/java/com/baeldung/networking/proxies/DirectProxyDemo.java

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+package com.baeldung.networking.proxies;
+
+import java.io.IOException;
+import java.net.HttpURLConnection;
+import java.net.Proxy;
+import java.net.URL;
+
+public class DirectProxyDemo {
+
+    private static final String URL_STRING = "http://www.google.com";
+
+    public static void main(String... args) throws IOException {
+
+        URL weburl = new URL(URL_STRING);
+        HttpURLConnection directConnection 
+          = (HttpURLConnection) weburl.openConnection(Proxy.NO_PROXY);
+        System.out.println(UrlConnectionUtils.contentAsString(directConnection));
+    }
+
+}

core-java-modules/core-java-networking/src/main/java/com/baeldung/networking/proxies/SocksProxyDemo.java

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+package com.baeldung.networking.proxies;
+
+import java.io.IOException;
+import java.net.HttpURLConnection;
+import java.net.InetSocketAddress;
+import java.net.Proxy;
+import java.net.Socket;
+import java.net.URL;
+
+public class SocksProxyDemo {
+
+    private static final String URL_STRING = "http://www.google.com";
+    private static final String SOCKET_SERVER_HOST = "someserver.baeldung.com";
+    private static final int SOCKET_SERVER_PORT = 1111;
+
+    public static void main(String... args) throws IOException {
+
+        URL weburl = new URL(URL_STRING);
+        Proxy socksProxy 
+          = new Proxy(Proxy.Type.SOCKS, new InetSocketAddress("127.0.0.1", 1080));
+        HttpURLConnection socksConnection 
+          = (HttpURLConnection) weburl.openConnection(socksProxy);
+        System.out.println(UrlConnectionUtils.contentAsString(socksConnection));
+
+        Socket proxySocket = new Socket(socksProxy);
+        InetSocketAddress socketHost 
+          = new InetSocketAddress(SOCKET_SERVER_HOST, SOCKET_SERVER_PORT);
+        proxySocket.connect(socketHost);
+        // do stuff with the socket
+    }
+
+}

core-java-modules/core-java-networking/src/main/java/com/baeldung/networking/proxies/SystemPropertyProxyDemo.java

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+package com.baeldung.networking.proxies;
+
+import java.net.URL;
+import java.net.URLConnection;
+
+public class SystemPropertyProxyDemo {
+
+    public static final String RESOURCE_URL = "http://www.google.com";
+
+    public static void main(String[] args) throws Exception {
+
+        System.setProperty("http.proxyHost", "127.0.0.1");
+        System.setProperty("http.proxyPort", "3128");
+
+        URL url = new URL(RESOURCE_URL);
+        URLConnection con = url.openConnection();
+        System.out.println(UrlConnectionUtils.contentAsString(con));
+
+        System.setProperty("http.proxyHost", null);
+        // proxy will no longer be used for http connections
+    }
+
+}

core-java-modules/core-java-networking/src/main/java/com/baeldung/networking/proxies/UrlConnectionUtils.java

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+package com.baeldung.networking.proxies;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.net.URLConnection;
+
+class UrlConnectionUtils {
+
+    public static String contentAsString(URLConnection con) throws IOException {
+        StringBuilder builder = new StringBuilder();
+        try (BufferedReader reader 
+                = new BufferedReader(new InputStreamReader(con.getInputStream()))){
+            while (reader.ready()) {
+                builder.append(reader.readLine());
+            }
+        }
+        return builder.toString();
+    }
+
+}

core-java-modules/core-java-networking/src/main/java/com/baeldung/networking/proxies/WebProxyDemo.java

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+package com.baeldung.networking.proxies;
+
+import java.io.IOException;
+import java.net.HttpURLConnection;
+import java.net.InetSocketAddress;
+import java.net.Proxy;
+import java.net.URL;
+
+public class WebProxyDemo {
+
+    private static final String URL_STRING = "http://www.google.com";
+
+    public static void main(String... args) throws IOException {
+
+        URL weburl = new URL(URL_STRING);
+        Proxy webProxy 
+          = new Proxy(Proxy.Type.HTTP, new InetSocketAddress("127.0.0.1", 3128));
+        HttpURLConnection webProxyConnection 
+            = (HttpURLConnection) weburl.openConnection(webProxy);
+        System.out.println(UrlConnectionUtils.contentAsString(webProxyConnection));
+    }
+
+}

core-java-modules/core-java-networking/src/main/java/com/baeldung/networking/udp/EchoClient.java

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+package com.baeldung.networking.udp;
+
+import java.io.IOException;
+import java.net.DatagramPacket;
+import java.net.DatagramSocket;
+import java.net.InetAddress;
+
+public class EchoClient {
+    private DatagramSocket socket;
+    private InetAddress address;
+
+    private byte[] buf;
+
+    public EchoClient() {
+        try {
+            socket = new DatagramSocket();
+            address = InetAddress.getByName("localhost");
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+
+    }
+
+    public String sendEcho(String msg) {
+        DatagramPacket packet = null;
+        try {
+            buf = msg.getBytes();
+            packet = new DatagramPacket(buf, buf.length, address, 4445);
+            socket.send(packet);
+            packet = new DatagramPacket(buf, buf.length);
+            socket.receive(packet);
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+        String received = new String(packet.getData(), 0, packet.getLength());
+        return received;
+    }
+
+    public void close() {
+        socket.close();
+    }
+}

core-java-modules/core-java-networking/src/main/java/com/baeldung/networking/udp/EchoServer.java

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+package com.baeldung.networking.udp;
+
+import java.io.IOException;
+import java.net.DatagramPacket;
+import java.net.DatagramSocket;
+import java.net.InetAddress;
+
+public class EchoServer extends Thread {
+
+    protected DatagramSocket socket = null;
+    protected boolean running;
+    protected byte[] buf = new byte[256];
+
+    public EchoServer() throws IOException {
+        socket = new DatagramSocket(4445);
+    }
+
+    public void run() {
+        running = true;
+
+        while (running) {
+            try {
+
+                DatagramPacket packet = new DatagramPacket(buf, buf.length);
+                socket.receive(packet);
+                InetAddress address = packet.getAddress();
+                int port = packet.getPort();
+                packet = new DatagramPacket(buf, buf.length, address, port);
+                String received = new String(packet.getData(), 0, packet.getLength());
+                if (received.equals("end")) {
+                    running = false;
+                    continue;
+                }
+                socket.send(packet);
+            } catch (IOException e) {
+                e.printStackTrace();
+                running = false;
+            }
+        }
+        socket.close();
+    }
+}

core-java-modules/core-java-networking/src/main/java/com/baeldung/networking/udp/broadcast/BroadcastingClient.java

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+package com.baeldung.networking.udp.broadcast;
+
+import java.io.IOException;
+import java.net.DatagramPacket;
+import java.net.DatagramSocket;
+import java.net.InetAddress;
+import java.net.NetworkInterface;
+import java.net.SocketException;
+import java.util.ArrayList;
+import java.util.Enumeration;
+import java.util.List;
+import java.util.stream.Collectors;
+
+public class BroadcastingClient {
+    private DatagramSocket socket;
+    private InetAddress address;
+    private int expectedServerCount;
+    private byte[] buf;
+
+    public BroadcastingClient(int expectedServerCount) throws Exception {
+        this.expectedServerCount = expectedServerCount;
+        this.address = InetAddress.getByName("255.255.255.255");
+    }
+
+    public int discoverServers(String msg) throws IOException {
+        initializeSocketForBroadcasting();
+        copyMessageOnBuffer(msg);
+
+        // When we want to broadcast not just to local network, call listAllBroadcastAddresses() and execute broadcastPacket for each value.
+        broadcastPacket(address);
+
+        return receivePackets();
+    }
+
+    List<InetAddress> listAllBroadcastAddresses() throws SocketException {
+        List<InetAddress> broadcastList = new ArrayList<>();
+        Enumeration<NetworkInterface> interfaces = NetworkInterface.getNetworkInterfaces();
+        while (interfaces.hasMoreElements()) {
+            NetworkInterface networkInterface = interfaces.nextElement();
+
+            if (networkInterface.isLoopback() || !networkInterface.isUp()) {
+                continue;
+            }
+
+            broadcastList.addAll(networkInterface.getInterfaceAddresses()
+                .stream()
+                .filter(address -> address.getBroadcast() != null)
+                .map(address -> address.getBroadcast())
+                .collect(Collectors.toList()));
+        }
+        return broadcastList;
+    }
+
+    private void initializeSocketForBroadcasting() throws SocketException {
+        socket = new DatagramSocket();
+        socket.setBroadcast(true);
+    }
+
+    private void copyMessageOnBuffer(String msg) {
+        buf = msg.getBytes();
+    }
+
+    private void broadcastPacket(InetAddress address) throws IOException {
+        DatagramPacket packet = new DatagramPacket(buf, buf.length, address, 4445);
+        socket.send(packet);
+    }
+
+    private int receivePackets() throws IOException {
+        int serversDiscovered = 0;
+        while (serversDiscovered != expectedServerCount) {
+            receivePacket();
+            serversDiscovered++;
+        }
+        return serversDiscovered;
+    }
+
+    private void receivePacket() throws IOException {
+        DatagramPacket packet = new DatagramPacket(buf, buf.length);
+        socket.receive(packet);
+    }
+
+    public void close() {
+        socket.close();
+    }
+}

core-java-modules/core-java-networking/src/main/java/com/baeldung/networking/udp/broadcast/BroadcastingEchoServer.java

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+package com.baeldung.networking.udp.broadcast;
+
+import java.io.IOException;
+import java.net.DatagramPacket;
+import java.net.DatagramSocket;
+import java.net.InetAddress;
+import java.net.InetSocketAddress;
+
+public class BroadcastingEchoServer extends Thread {
+
+    protected DatagramSocket socket = null;
+    protected boolean running;
+    protected byte[] buf = new byte[256];
+
+    public BroadcastingEchoServer() throws IOException {
+        socket = new DatagramSocket(null);
+        socket.setReuseAddress(true);
+        socket.bind(new InetSocketAddress(4445));
+    }
+
+    public void run() {
+        running = true;
+
+        while (running) {
+            try {
+                DatagramPacket packet = new DatagramPacket(buf, buf.length);
+                socket.receive(packet);
+                InetAddress address = packet.getAddress();
+                int port = packet.getPort();
+                packet = new DatagramPacket(buf, buf.length, address, port);
+                String received = new String(packet.getData(), 0, packet.getLength());
+                if (received.equals("end")) {
+                    running = false;
+                    continue;
+                }
+                socket.send(packet);
+            } catch (IOException e) {
+                e.printStackTrace();
+                running = false;
+            }
+        }
+        socket.close();
+    }
+}

core-java-modules/core-java-networking/src/main/java/com/baeldung/networking/udp/multicast/MulticastEchoServer.java

@@ -0,0 +1,41 @@
+package com.baeldung.networking.udp.multicast;
+
+import java.io.IOException;
+import java.net.DatagramPacket;
+import java.net.InetAddress;
+import java.net.MulticastSocket;
+
+public class MulticastEchoServer extends Thread {
+
+    protected MulticastSocket socket = null;
+    protected byte[] buf = new byte[256];
+    protected InetAddress group = null;
+
+    public MulticastEchoServer() throws IOException {
+        socket = new MulticastSocket(4446);
+        socket.setReuseAddress(true);
+        group = InetAddress.getByName("230.0.0.0");
+        socket.joinGroup(group);
+    }
+
+    public void run() {
+        try {
+            while (true) {
+                DatagramPacket packet = new DatagramPacket(buf, buf.length);
+                socket.receive(packet);
+                InetAddress address = packet.getAddress();
+                int port = packet.getPort();
+                packet = new DatagramPacket(buf, buf.length, address, port);
+                String received = new String(packet.getData(), 0, packet.getLength());
+                if (received.equals("end")) {
+                    break;
+                }
+                socket.send(packet);
+            }
+            socket.leaveGroup(group);
+            socket.close();
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
+}

core-java-modules/core-java-networking/src/main/java/com/baeldung/networking/udp/multicast/MulticastingClient.java

@@ -0,0 +1,53 @@
+package com.baeldung.networking.udp.multicast;
+
+import java.io.IOException;
+import java.net.DatagramPacket;
+import java.net.DatagramSocket;
+import java.net.InetAddress;
+
+public class MulticastingClient {
+    private DatagramSocket socket;
+    private InetAddress group;
+    private int expectedServerCount;
+    private byte[] buf;
+
+    public MulticastingClient(int expectedServerCount) throws Exception {
+        this.expectedServerCount = expectedServerCount;
+        this.socket = new DatagramSocket();
+        this.group = InetAddress.getByName("230.0.0.0");
+    }
+
+    public int discoverServers(String msg) throws IOException {
+        copyMessageOnBuffer(msg);
+        multicastPacket();
+
+        return receivePackets();
+    }
+
+    private void copyMessageOnBuffer(String msg) {
+        buf = msg.getBytes();
+    }
+
+    private void multicastPacket() throws IOException {
+        DatagramPacket packet = new DatagramPacket(buf, buf.length, group, 4446);
+        socket.send(packet);
+    }
+
+    private int receivePackets() throws IOException {
+        int serversDiscovered = 0;
+        while (serversDiscovered != expectedServerCount) {
+            receivePacket();
+            serversDiscovered++;
+        }
+        return serversDiscovered;
+    }
+
+    private void receivePacket() throws IOException {
+        DatagramPacket packet = new DatagramPacket(buf, buf.length);
+        socket.receive(packet);
+    }
+
+    public void close() {
+        socket.close();
+    }
+}

core-java-modules/core-java-networking/src/main/java/com/baeldung/networking/uriurl/URIDemo.java

@@ -0,0 +1,91 @@
+package com.baeldung.networking.uriurl;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.net.MalformedURLException;
+import java.net.URI;
+import java.net.URISyntaxException;
+import java.net.URL;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class URIDemo {
+    private final Logger logger = LoggerFactory.getLogger(URIDemo.class);
+
+    String URISTRING = "https://wordpress.org:443/support/topic/page-jumps-within-wordpress/?replies=3#post-2278484";
+    // parsed locator
+    String URISCHEME = "https";
+    String URISCHEMESPECIFIC;
+    String URIHOST = "wordpress.org";
+    String URIAUTHORITY = "wordpress.org:443";
+
+    String URIPATH = "/support/topic/page-jumps-within-wordpress/";
+    int URIPORT = 443;
+    String URIQUERY = "replies=3";
+    String URIFRAGMENT = "post-2278484";
+    String URIUSERINFO;
+    String URICOMPOUND = URISCHEME + "://" + URIHOST + ":" + URIPORT + URIPATH + "?" + URIQUERY + "#" + URIFRAGMENT;
+
+    URI uri;
+    URL url;
+    BufferedReader in = null;
+    String URIContent = "";
+
+    private String getParsedPieces(URI uri) {
+        logger.info("*** List of parsed pieces ***");
+        URISCHEME = uri.getScheme();
+        logger.info("URISCHEME: " + URISCHEME);
+        URISCHEMESPECIFIC = uri.getSchemeSpecificPart();
+        logger.info("URISCHEMESPECIFIC: " + URISCHEMESPECIFIC);
+        URIHOST = uri.getHost();
+        URIAUTHORITY = uri.getAuthority();
+        logger.info("URIAUTHORITY: " + URIAUTHORITY);
+        logger.info("URIHOST: " + URIHOST);
+        URIPATH = uri.getPath();
+        logger.info("URIPATH: " + URIPATH);
+        URIPORT = uri.getPort();
+        logger.info("URIPORT: " + URIPORT);
+        URIQUERY = uri.getQuery();
+        logger.info("URIQUERY: " + URIQUERY);
+        URIFRAGMENT = uri.getFragment();
+        logger.info("URIFRAGMENT: " + URIFRAGMENT);
+
+        try {
+            url = uri.toURL();
+        } catch (MalformedURLException e) {
+            logger.info("MalformedURLException thrown: " + e.getMessage());
+            e.printStackTrace();
+        } catch (IllegalArgumentException e) {
+            logger.info("IllegalArgumentException thrown: " + e.getMessage());
+            e.printStackTrace();
+        }
+        return url.toString();
+    }
+
+    public String testURIAsNew(String URIString) {
+        // creating URI object
+        try {
+            uri = new URI(URIString);
+        } catch (URISyntaxException e) {
+            logger.info("URISyntaxException thrown: " + e.getMessage());
+            e.printStackTrace();
+            throw new IllegalArgumentException();
+        }
+        return getParsedPieces(uri);
+    }
+
+    public String testURIAsCreate(String URIString) {
+        // creating URI object
+        uri = URI.create(URIString);
+        return getParsedPieces(uri);
+    }
+
+    public static void main(String[] args) throws Exception {
+        URIDemo demo = new URIDemo();
+        String contentCreate = demo.testURIAsCreate(demo.URICOMPOUND);
+        demo.logger.info(contentCreate);
+        String contentNew = demo.testURIAsNew(demo.URICOMPOUND);
+        demo.logger.info(contentNew);
+    }
+}

core-java-modules/core-java-networking/src/main/java/com/baeldung/networking/uriurl/URLDemo.java

@@ -0,0 +1,70 @@
+package com.baeldung.networking.uriurl;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.net.HttpURLConnection;
+import java.net.URI;
+import java.net.URL;
+import java.net.URLConnection;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class URLDemo {
+    private final Logger log = LoggerFactory.getLogger(URLDemo.class);
+
+    String URLSTRING = "https://wordpress.org:443/support/topic/page-jumps-within-wordpress/?replies=3#post-2278484";
+    // parsed locator
+    String URLPROTOCOL = "https";
+    // final static String URLAUTHORITY = "wordpress.org:443";
+    String URLHOST = "wordpress.org";
+    String URLPATH = "/support/topic/page-jumps-within-wordpress/";
+    // final static String URLFILENAME = "/support/topic/page-jumps-within-wordpress/?replies=3";
+    // final static int URLPORT = 443;
+    int URLDEFAULTPORT = 443;
+    String URLQUERY = "replies=3";
+    String URLREFERENCE = "post-2278484";
+    String URLCOMPOUND = URLPROTOCOL + "://" + URLHOST + ":" + URLDEFAULTPORT + URLPATH + "?" + URLQUERY + "#" + URLREFERENCE;
+
+    URL url;
+    URLConnection urlConnection = null;
+    HttpURLConnection connection = null;
+    BufferedReader in = null;
+    String urlContent = "";
+
+    public String testURL(String urlString) throws IOException, IllegalArgumentException {
+        String urlStringCont = "";
+        // comment the if clause if experiment with URL
+        /*if (!URLSTRING.equals(urlString)) {
+            throw new IllegalArgumentException("URL String argument is not proper: " + urlString);
+        }*/
+        // creating URL object
+        url = new URL(urlString);
+        // get URL connection
+        urlConnection = url.openConnection();
+        connection = null;
+        // we can check, if connection is proper type
+        if (urlConnection instanceof HttpURLConnection) {
+            connection = (HttpURLConnection) urlConnection;
+        } else {
+            log.info("Please enter an HTTP URL");
+            throw new IOException("HTTP URL is not correct");
+        }
+        // we can check response code (200 OK is expected)
+        log.info(connection.getResponseCode() + " " + connection.getResponseMessage());
+        in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
+        String current;
+
+        while ((current = in.readLine()) != null) {
+            urlStringCont += current;
+        }
+        return urlStringCont;
+    }
+
+    public static void main(String[] args) throws Exception {
+        URLDemo demo = new URLDemo();
+        String content = demo.testURL(demo.URLCOMPOUND);
+        demo.log.info(content);
+    }
+}

core-java-modules/core-java-networking/src/main/java/com/baeldung/socket/EchoClient.java

@@ -0,0 +1,47 @@
+package com.baeldung.socket;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.*;
+import java.net.*;
+
+public class EchoClient {
+
+    private static final Logger LOG = LoggerFactory.getLogger(EchoClient.class);
+
+    private Socket clientSocket;
+    private PrintWriter out;
+    private BufferedReader in;
+
+    public void startConnection(String ip, int port) {
+        try {
+            clientSocket = new Socket(ip, port);
+            out = new PrintWriter(clientSocket.getOutputStream(), true);
+            in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
+        } catch (IOException e) {
+            LOG.debug("Error when initializing connection", e);
+        }
+
+    }
+
+    public String sendMessage(String msg) {
+        try {
+            out.println(msg);
+            return in.readLine();
+        } catch (Exception e) {
+            return null;
+        }
+    }
+
+    public void stopConnection() {
+        try {
+            in.close();
+            out.close();
+            clientSocket.close();
+        } catch (IOException e) {
+            LOG.debug("error when closing", e);
+        }
+
+    }
+}

core-java-modules/core-java-networking/src/main/java/com/baeldung/socket/EchoMultiServer.java

@@ -0,0 +1,76 @@
+package com.baeldung.socket;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.net.*;
+import java.io.*;
+
+public class EchoMultiServer {
+
+    private static final Logger LOG = LoggerFactory.getLogger(EchoMultiServer.class);
+
+    private ServerSocket serverSocket;
+
+    public void start(int port) {
+        try {
+            serverSocket = new ServerSocket(port);
+            while (true)
+                new EchoClientHandler(serverSocket.accept()).start();
+
+        } catch (IOException e) {
+            e.printStackTrace();
+        } finally {
+            stop();
+        }
+
+    }
+
+    public void stop() {
+        try {
+
+            serverSocket.close();
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+
+    }
+
+    private static class EchoClientHandler extends Thread {
+        private Socket clientSocket;
+        private PrintWriter out;
+        private BufferedReader in;
+
+        public EchoClientHandler(Socket socket) {
+            this.clientSocket = socket;
+        }
+
+        public void run() {
+            try {
+                out = new PrintWriter(clientSocket.getOutputStream(), true);
+                in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
+                String inputLine;
+                while ((inputLine = in.readLine()) != null) {
+                    if (".".equals(inputLine)) {
+                        out.println("bye");
+                        break;
+                    }
+                    out.println(inputLine);
+                }
+
+                in.close();
+                out.close();
+                clientSocket.close();
+
+            } catch (IOException e) {
+                LOG.debug(e.getMessage());
+            }
+        }
+    }
+
+    public static void main(String[] args) {
+        EchoMultiServer server = new EchoMultiServer();
+        server.start(5555);
+    }
+
+}

core-java-modules/core-java-networking/src/main/java/com/baeldung/socket/EchoServer.java

@@ -0,0 +1,55 @@
+package com.baeldung.socket;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.net.*;
+import java.io.*;
+
+public class EchoServer {
+
+    private static final Logger LOG = LoggerFactory.getLogger(EchoServer.class);
+
+    private ServerSocket serverSocket;
+    private Socket clientSocket;
+    private PrintWriter out;
+    private BufferedReader in;
+
+    public void start(int port) {
+        try {
+            serverSocket = new ServerSocket(port);
+            clientSocket = serverSocket.accept();
+            out = new PrintWriter(clientSocket.getOutputStream(), true);
+            in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
+            String inputLine;
+            while ((inputLine = in.readLine()) != null) {
+                if (".".equals(inputLine)) {
+                    out.println("good bye");
+                    break;
+                }
+                out.println(inputLine);
+            }
+        } catch (IOException e) {
+            LOG.debug(e.getMessage());
+        }
+
+    }
+
+    public void stop() {
+        try {
+            in.close();
+            out.close();
+            clientSocket.close();
+            serverSocket.close();
+        } catch (IOException e) {
+            LOG.debug(e.getMessage());
+        }
+
+    }
+
+    public static void main(String[] args) {
+        EchoServer server = new EchoServer();
+        server.start(4444);
+    }
+
+}

core-java-modules/core-java-networking/src/main/java/com/baeldung/socket/GreetClient.java

@@ -0,0 +1,50 @@
+package com.baeldung.socket;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.PrintWriter;
+import java.net.Socket;
+
+public class GreetClient {
+
+    private static final Logger LOG = LoggerFactory.getLogger(EchoMultiServer.class);
+
+    private Socket clientSocket;
+    private PrintWriter out;
+    private BufferedReader in;
+
+    public void startConnection(String ip, int port) {
+        try {
+            clientSocket = new Socket(ip, port);
+            out = new PrintWriter(clientSocket.getOutputStream(), true);
+            in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
+        } catch (IOException e) {
+            LOG.debug(e.getMessage());
+        }
+
+    }
+
+    public String sendMessage(String msg) {
+        try {
+            out.println(msg);
+            return in.readLine();
+        } catch (Exception e) {
+            return null;
+        }
+    }
+
+    public void stopConnection() {
+        try {
+            in.close();
+            out.close();
+            clientSocket.close();
+        } catch (IOException e) {
+            LOG.debug(e.getMessage());
+        }
+    }
+
+}

core-java-modules/core-java-networking/src/main/java/com/baeldung/socket/GreetServer.java

@@ -0,0 +1,52 @@
+package com.baeldung.socket;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.net.*;
+import java.io.*;
+
+public class GreetServer {
+
+    private static final Logger LOG = LoggerFactory.getLogger(GreetServer.class);
+
+    private ServerSocket serverSocket;
+    private Socket clientSocket;
+    private PrintWriter out;
+    private BufferedReader in;
+
+    public void start(int port) {
+        try {
+            serverSocket = new ServerSocket(port);
+            clientSocket = serverSocket.accept();
+            out = new PrintWriter(clientSocket.getOutputStream(), true);
+            in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
+            String greeting = in.readLine();
+            if ("hello server".equals(greeting))
+                out.println("hello client");
+            else
+                out.println("unrecognised greeting");
+        } catch (IOException e) {
+            LOG.debug(e.getMessage());
+        }
+
+    }
+
+    public void stop() {
+        try {
+            in.close();
+            out.close();
+            clientSocket.close();
+            serverSocket.close();
+        } catch (IOException e) {
+            LOG.debug(e.getMessage());
+        }
+
+    }
+
+    public static void main(String[] args) {
+        GreetServer server = new GreetServer();
+        server.start(6666);
+    }
+
+}

core-java-modules/core-java-networking/src/main/java/com/baeldung/socket/read/Client.java

@@ -0,0 +1,29 @@
+package com.baeldung.socket.read;
+
+import java.net.*;
+import java.nio.charset.StandardCharsets;
+import java.io.*; 
+
+public class Client {
+    
+    public void runClient(String ip, int port) {
+        try {
+            Socket socket = new Socket(ip, port);
+            System.out.println("Connected to server ...");
+            DataInputStream in = new DataInputStream(System.in);
+            DataOutputStream out = new DataOutputStream(socket.getOutputStream());
+            
+            char type = 's'; // s for string
+            int length = 29;
+            String data = "This is a string of length 29";
+            byte[] dataInBytes = data.getBytes(StandardCharsets.UTF_8);         
+            //Sending data in TLV format        
+            out.writeChar(type);
+            out.writeInt(length);
+            out.write(dataInBytes);
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
+
+}

core-java-modules/core-java-networking/src/main/java/com/baeldung/socket/read/Server.java

@@ -0,0 +1,49 @@
+package com.baeldung.socket.read;
+
+import java.net.*;
+import java.nio.charset.StandardCharsets;
+import java.io.*; 
+
+public class Server {
+    
+    public void runServer(int port) {
+        //Start the server and wait for connection
+        try {
+            ServerSocket server = new ServerSocket(port);
+            System.out.println("Server Started. Waiting for connection ...");
+            Socket socket = server.accept();
+            System.out.println("Got connection from client.");
+            //Get input stream from socket variable and convert the same to DataInputStream
+            DataInputStream in = new DataInputStream(new BufferedInputStream(socket.getInputStream()));
+            //Read type and length of data
+            char dataType = in.readChar();
+            int length = in.readInt();
+            System.out.println("Type : "+dataType);
+            System.out.println("Lenght :"+length);
+            if(dataType == 's') {
+                //Read String data in bytes
+                byte[] messageByte = new byte[length];
+                boolean end = false;
+                StringBuilder dataString = new StringBuilder(length);
+                int totalBytesRead = 0;
+                //We need to run while loop, to read all data in that stream
+                while(!end) {
+                    int currentBytesRead = in.read(messageByte);
+                    totalBytesRead = currentBytesRead + totalBytesRead;
+                    if(totalBytesRead <= length) {
+                        dataString.append(new String(messageByte,0,currentBytesRead,StandardCharsets.UTF_8));
+                    } else {
+                        dataString.append(new String(messageByte,0,length - totalBytesRead + currentBytesRead,StandardCharsets.UTF_8));
+                    }
+                    if(dataString.length()>=length) {
+                        end = true;
+                    }
+                }
+                System.out.println("Read "+length+" bytes of message from client. Message = "+dataString);
+            }
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+    }
+
+}

core-java-modules/core-java-networking/src/main/resources/logback.xml

@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<configuration>
+    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
+        <encoder>
+            <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n
+            </pattern>
+        </encoder>
+    </appender>
+
+    <logger name="org.springframework" level="WARN" />
+    <logger name="org.springframework.transaction" level="WARN" />
+
+    <!-- in order to debug some marshalling issues, this needs to be TRACE -->
+    <logger name="org.springframework.web.servlet.mvc" level="WARN" />
+
+    <root level="INFO">
+        <appender-ref ref="STDOUT" />
+    </root>
+</configuration>

core-java-modules/core-java-networking/src/test/java/com/baeldung/encoderdecoder/EncoderDecoderUnitTest.java

@@ -0,0 +1,112 @@
+package com.baeldung.encoderdecoder;
+
+import static java.util.stream.Collectors.joining;
+import static org.hamcrest.CoreMatchers.is;
+
+import java.io.UnsupportedEncodingException;
+import java.net.URL;
+import java.net.URLDecoder;
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.Map;
+
+import org.hamcrest.CoreMatchers;
+import org.junit.Assert;
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.web.util.UriUtils;
+
+public class EncoderDecoderUnitTest {
+
+    private static final Logger LOGGER = LoggerFactory.getLogger(EncoderDecoderUnitTest.class);
+    private static final String testUrl = "http://www.baeldung.com?key1=value+1&key2=value%40%21%242&key3=value%253";
+    private static final String testUrlWithPath = "http://www.baeldung.com/path+1?key1=value+1&key2=value%40%21%242&key3=value%253";
+
+    private String encodeValue(String value) {
+        String encoded = null;
+        try {
+            encoded = URLEncoder.encode(value, StandardCharsets.UTF_8.toString());
+        } catch (UnsupportedEncodingException e) {
+            LOGGER.error("Error encoding parameter {}", e.getMessage(), e);
+        }
+        return encoded;
+    }
+
+    private String decode(String value) {
+        String decoded = null;
+        try {
+            decoded = URLDecoder.decode(value, StandardCharsets.UTF_8.toString());
+        } catch (UnsupportedEncodingException e) {
+            LOGGER.error("Error encoding parameter {}", e.getMessage(), e);
+        }
+        return decoded;
+    }
+
+    @Test
+    public void givenURL_whenAnalyze_thenCorrect() throws Exception {
+        URL url = new URL(testUrl);
+
+        Assert.assertThat(url.getProtocol(), is("http"));
+        Assert.assertThat(url.getHost(), is("www.baeldung.com"));
+        Assert.assertThat(url.getQuery(), is("key1=value+1&key2=value%40%21%242&key3=value%253"));
+    }
+
+    @Test
+    public void givenRequestParam_whenUTF8Scheme_thenEncode() throws Exception {
+        Map<String, String> requestParams = new HashMap<>();
+        requestParams.put("key1", "value 1");
+        requestParams.put("key2", "value@!$2");
+        requestParams.put("key3", "value%3");
+
+        String encodedURL = requestParams.keySet().stream().map(key -> key + "=" + encodeValue(requestParams.get(key))).collect(joining("&", "http://www.baeldung.com?", ""));
+
+        Assert.assertThat(testUrl, is(encodedURL));
+    }
+
+    @Test
+    public void givenRequestParam_whenUTF8Scheme_thenDecodeRequestParams() throws Exception {
+        URL url = new URL(testUrl);
+
+        String query = url.getQuery();
+
+        String decodedQuery = Arrays.stream(query.split("&")).map(param -> param.split("=")[0] + "=" + decode(param.split("=")[1])).collect(joining("&"));
+
+        Assert.assertEquals("http://www.baeldung.com?key1=value 1&key2=value@!$2&key3=value%3", url.getProtocol() + "://" + url.getHost() + "?" + decodedQuery);
+    }
+
+    private String encodePath(String path) {
+        try {
+            path = UriUtils.encodePath(path, "UTF-8");
+        } catch (UnsupportedEncodingException e) {
+            LOGGER.error("Error encoding parameter {}", e.getMessage(), e);
+        }
+        return path;
+    }
+
+    @Test
+    public void givenPathSegment_thenEncodeDecode() throws UnsupportedEncodingException {
+        String pathSegment = "/Path 1/Path+2";
+        String encodedPathSegment = encodePath(pathSegment);
+        String decodedPathSegment = UriUtils.decode(encodedPathSegment, "UTF-8");
+        Assert.assertEquals("/Path%201/Path+2", encodedPathSegment);
+        Assert.assertEquals("/Path 1/Path+2", decodedPathSegment);
+    }
+
+    @Test
+    public void givenPathAndRequestParam_whenUTF8Scheme_thenEncode() throws Exception {
+        Map<String, String> requestParams = new HashMap<>();
+        requestParams.put("key1", "value 1");
+        requestParams.put("key2", "value@!$2");
+        requestParams.put("key3", "value%3");
+
+        String path = "path+1";
+
+        String encodedURL = requestParams.keySet().stream().map(key -> key + "=" + encodeValue(requestParams.get(key))).collect(joining("&", "http://www.baeldung.com/" + encodePath(path) + "?", ""));
+
+        Assert.assertThat(testUrlWithPath, is(encodedURL));
+    }
+
+}

core-java-modules/core-java-networking/src/test/java/com/baeldung/networking/interfaces/NetworkInterfaceManualTest.java

@@ -0,0 +1,118 @@
+package com.baeldung.networking.interfaces;
+
+import org.junit.Test;
+
+import java.net.*;
+import java.util.Enumeration;
+import java.util.List;
+
+import static org.junit.Assert.*;
+
+public class NetworkInterfaceManualTest {
+    @Test
+    public void givenName_whenReturnsNetworkInterface_thenCorrect() throws SocketException {
+        NetworkInterface nif = NetworkInterface.getByName("lo");
+        assertNotNull(nif);
+    }
+
+    @Test
+    public void givenInExistentName_whenReturnsNull_thenCorrect() throws SocketException {
+        NetworkInterface nif = NetworkInterface.getByName("inexistent_name");
+        assertNull(nif);
+    }
+
+    @Test
+    public void givenIP_whenReturnsNetworkInterface_thenCorrect() throws SocketException, UnknownHostException {
+        byte[] ip = new byte[] { 127, 0, 0, 1 };
+        NetworkInterface nif = NetworkInterface.getByInetAddress(InetAddress.getByAddress(ip));
+        assertNotNull(nif);
+    }
+
+    @Test
+    public void givenHostName_whenReturnsNetworkInterface_thenCorrect() throws SocketException, UnknownHostException {
+        NetworkInterface nif = NetworkInterface.getByInetAddress(InetAddress.getByName("localhost"));
+        assertNotNull(nif);
+    }
+
+    @Test
+    public void givenLocalHost_whenReturnsNetworkInterface_thenCorrect() throws SocketException, UnknownHostException {
+        NetworkInterface nif = NetworkInterface.getByInetAddress(InetAddress.getLocalHost());
+        assertNotNull(nif);
+    }
+
+    @Test
+    public void givenLoopBack_whenReturnsNetworkInterface_thenCorrect() throws SocketException, UnknownHostException {
+        NetworkInterface nif = NetworkInterface.getByInetAddress(InetAddress.getLoopbackAddress());
+        assertNotNull(nif);
+    }
+
+    @Test
+    public void givenIndex_whenReturnsNetworkInterface_thenCorrect() throws SocketException, UnknownHostException {
+        NetworkInterface nif = NetworkInterface.getByIndex(0);
+        assertNotNull(nif);
+    }
+
+    @Test
+    public void givenInterface_whenReturnsInetAddresses_thenCorrect() throws SocketException, UnknownHostException {
+        NetworkInterface nif = NetworkInterface.getByName("lo");
+        Enumeration<InetAddress> addressEnum = nif.getInetAddresses();
+        InetAddress address = addressEnum.nextElement();
+        assertEquals("127.0.0.1", address.getHostAddress());
+    }
+
+    @Test
+    public void givenInterface_whenReturnsInterfaceAddresses_thenCorrect() throws SocketException, UnknownHostException {
+        NetworkInterface nif = NetworkInterface.getByName("lo");
+
+        List<InterfaceAddress> addressEnum = nif.getInterfaceAddresses();
+        InterfaceAddress address = addressEnum.get(0);
+        InetAddress localAddress = address.getAddress();
+        InetAddress broadCastAddress = address.getBroadcast();
+        assertEquals("127.0.0.1", localAddress.getHostAddress());
+        assertEquals("127.255.255.255", broadCastAddress.getHostAddress());
+    }
+
+    @Test
+    public void givenInterface_whenChecksIfLoopback_thenCorrect() throws SocketException, UnknownHostException {
+        NetworkInterface nif = NetworkInterface.getByName("lo");
+        assertTrue(nif.isLoopback());
+    }
+
+    @Test
+    public void givenInterface_whenChecksIfUp_thenCorrect() throws SocketException, UnknownHostException {
+        NetworkInterface nif = NetworkInterface.getByName("lo");
+        assertTrue(nif.isUp());
+    }
+
+    @Test
+    public void givenInterface_whenChecksIfPointToPoint_thenCorrect() throws SocketException, UnknownHostException {
+        NetworkInterface nif = NetworkInterface.getByName("lo");
+        assertFalse(nif.isPointToPoint());
+    }
+
+    @Test
+    public void givenInterface_whenChecksIfVirtual_thenCorrect() throws SocketException, UnknownHostException {
+        NetworkInterface nif = NetworkInterface.getByName("lo");
+        assertFalse(nif.isVirtual());
+    }
+
+    @Test
+    public void givenInterface_whenChecksMulticastSupport_thenCorrect() throws SocketException, UnknownHostException {
+        NetworkInterface nif = NetworkInterface.getByName("lo");
+        assertTrue(nif.supportsMulticast());
+    }
+
+    @Test
+    public void givenInterface_whenGetsMacAddress_thenCorrect() throws SocketException, UnknownHostException {
+        NetworkInterface nif = NetworkInterface.getByName("lo");
+        byte[] bytes = nif.getHardwareAddress();
+        assertNotNull(bytes);
+    }
+
+    @Test
+    public void givenInterface_whenGetsMTU_thenCorrect() throws SocketException, UnknownHostException {
+        NetworkInterface nif = NetworkInterface.getByName("net0");
+        int mtu = nif.getMTU();
+        assertEquals(1500, mtu);
+    }
+}

core-java-modules/core-java-networking/src/test/java/com/baeldung/networking/udp/UDPLiveTest.java

@@ -0,0 +1,38 @@
+package com.baeldung.networking.udp;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.io.IOException;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+
+public class UDPLiveTest {
+    private EchoClient client;
+
+    @Before
+    public void setup() throws IOException {
+        new EchoServer().start();
+        client = new EchoClient();
+    }
+
+    @Test
+    public void whenCanSendAndReceivePacket_thenCorrect1() {
+        String echo = client.sendEcho("hello server");
+        assertEquals("hello server", echo);
+        echo = client.sendEcho("server is working");
+        assertFalse(echo.equals("hello server"));
+    }
+
+    @After
+    public void tearDown() {
+        stopEchoServer();
+        client.close();
+    }
+
+    private void stopEchoServer() {
+        client.sendEcho("end");
+    }
+}