added project code for sockets

sockets/pom.xml

@@ -0,0 +1,30 @@
+<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/maven-v4_0_0.xsd">
+	<modelVersion>4.0.0</modelVersion>
+	<groupId>com.baeldung</groupId>
+	<artifactId>sockets</artifactId>
+	<version>1.0</version>
+	<name>sockets</name>
+   <build>
+    <plugins>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-compiler-plugin</artifactId>
+        <version>3.3</version>
+        <configuration>
+          <source>7</source>
+          <target>7</target>
+        </configuration>
+      </plugin>
+    </plugins>
+  </build>
+	<dependencies>
+		<dependency>
+			<groupId>junit</groupId>
+			<artifactId>junit</artifactId>
+			<version>4.3</version>
+			<scope>test</scope>
+		</dependency>
+
+	</dependencies>
+</project>

sockets/src/main/java/com/baeldung/socket/EchoClient.java

@@ -0,0 +1,43 @@
+package com.baeldung.socket;
+
+import java.io.*;
+import java.net.*;
+
+public class EchoClient {
+	private Socket clientSocket = null;
+	private PrintWriter out = null;
+	private BufferedReader in = null;
+
+	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) {
+			
+		}
+
+	}
+
+	public String sendMessage(String msg) {
+		try {
+			out.println(msg);
+			String resp = in.readLine();
+			return resp;
+		} catch (Exception e) {
+			return null;
+		}
+	}
+
+	public void stopConnection() {
+		try {
+			in.close();
+			out.close();
+			clientSocket.close();
+		} catch (IOException e) {
+			e.printStackTrace();
+		}
+
+	}
+}

sockets/src/main/java/com/baeldung/socket/EchoMultiServer.java

@@ -0,0 +1,71 @@
+package com.baeldung.socket;
+
+import java.net.*;
+import java.io.*;
+
+public class EchoMultiServer {
+	private ServerSocket serverSocket = null;
+
+	public void start(int port) {
+		try {
+			serverSocket = new ServerSocket(port);
+			while (true)
+				new EchoClientHandler(serverSocket.accept()).run();
+
+		} 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 = null;
+		private BufferedReader in = null;
+
+		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) {
+				e.printStackTrace();
+			}
+		}
+	}
+
+	public static void main(String[] args) {
+		EchoMultiServer server = new EchoMultiServer();
+		server.start(5555);
+	}
+
+}

sockets/src/main/java/com/baeldung/socket/EchoServer.java

@@ -0,0 +1,50 @@
+package com.baeldung.socket;
+
+import java.net.*;
+import java.io.*;
+
+public class EchoServer {
+	private ServerSocket serverSocket = null;
+	private Socket clientSocket = null;
+	private PrintWriter out = null;
+	private BufferedReader in = null;
+
+	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) {
+			e.printStackTrace();
+		}
+
+	}
+
+	public void stop() {
+		try {
+			in.close();
+			out.close();
+			clientSocket.close();
+			serverSocket.close();
+		} catch (IOException e) {
+			e.printStackTrace();
+		}
+
+	}
+
+	public static void main(String[] args) {
+		EchoServer server = new EchoServer();
+		server.start(4444);
+	}
+
+}

sockets/src/main/java/com/baeldung/socket/GreetClient.java

@@ -0,0 +1,46 @@
+package com.baeldung.socket;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.PrintWriter;
+import java.net.Socket;
+
+public class GreetClient {
+	private Socket clientSocket = null;
+	private PrintWriter out = null;
+	private BufferedReader in = null;
+
+	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) {
+			
+		}
+
+	}
+
+	public String sendMessage(String msg) {
+		try {
+			out.println(msg);
+			String resp = in.readLine();
+			return resp;
+		} catch (Exception e) {
+			return null;
+		}
+	}
+
+	public void stopConnection() {
+		try {
+			in.close();
+			out.close();
+			clientSocket.close();
+		} catch (IOException e) {
+			e.printStackTrace();
+		}
+
+	}
+}

sockets/src/main/java/com/baeldung/socket/GreetServer.java

@@ -0,0 +1,47 @@
+package com.baeldung.socket;
+
+import java.net.*;
+import java.io.*;
+
+public class GreetServer {
+	private ServerSocket serverSocket = null;
+	private Socket clientSocket = null;
+	private PrintWriter out = null;
+	private BufferedReader in = null;
+
+
+	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 greetin");
+		} catch (IOException e) {
+			e.printStackTrace();
+		}
+
+	}
+
+	public void stop() {
+		try {
+			in.close();
+			out.close();
+			clientSocket.close();
+			serverSocket.close();
+		} catch (IOException e) {
+			e.printStackTrace();
+		}
+
+	}
+	public static void main(String[] args) {
+		GreetServer server=new GreetServer();
+		server.start(6666);
+	}
+
+}

sockets/src/test/java/com/baeldung/socket/EchoMultiTest.java

@@ -0,0 +1,44 @@
+package com.baeldung.socket;
+
+import static org.junit.Assert.*;
+
+import org.junit.Test;
+
+public class EchoMultiTest {
+	@Test
+	public void givenClient1_whenServerResponds_thenCorrect() {
+		EchoClient client1 = new EchoClient();
+		client1.startConnection("127.0.0.1", 5555);
+		String msg1 = client1.sendMessage("hello");
+		String msg2 = client1.sendMessage("world");
+		String terminate = client1.sendMessage(".");
+		assertEquals(msg1, "hello");
+		assertEquals(msg2, "world");
+		assertEquals(terminate, "bye");
+	}
+
+	@Test
+	public void givenClient2_whenServerResponds_thenCorrect() {
+		EchoClient client1 = new EchoClient();
+		client1.startConnection("127.0.0.1", 5555);
+		String msg1 = client1.sendMessage("hello");
+		String msg2 = client1.sendMessage("world");
+		String terminate = client1.sendMessage(".");
+		assertEquals(msg1, "hello");
+		assertEquals(msg2, "world");
+		assertEquals(terminate, "bye");
+	}
+
+	@Test
+	public void givenClient3_whenServerResponds_thenCorrect() {
+		EchoClient client1 = new EchoClient();
+		client1.startConnection("127.0.0.1", 5555);
+		String msg1 = client1.sendMessage("hello");
+		String msg2 = client1.sendMessage("world");
+		String terminate = client1.sendMessage(".");
+		assertEquals(msg1, "hello");
+		assertEquals(msg2, "world");
+		assertEquals(terminate, "bye");
+	}
+
+}

sockets/src/test/java/com/baeldung/socket/EchoTest.java

@@ -0,0 +1,36 @@
+package com.baeldung.socket;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+public class EchoTest {
+	EchoClient client = null;
+
+	@Before
+	public void setup() {
+		client = new EchoClient();
+		client.startConnection("127.0.0.1", 4444);
+	}
+
+	@Test
+	public void givenClient_whenServerEchosMessage_thenCorrect() {
+
+		String resp1 = client.sendMessage("hello");
+		String resp2 = client.sendMessage("world");
+		String resp3 = client.sendMessage("!");
+		String resp4 = client.sendMessage(".");
+		assertEquals("hello", resp1);
+		assertEquals("world", resp2);
+		assertEquals("!", resp3);
+		assertEquals("good bye", resp4);
+	}
+
+	@After
+	public void tearDown() {
+		client.stopConnection();
+	}
+
+}

sockets/src/test/java/com/baeldung/socket/GreetServerTest.java

@@ -0,0 +1,16 @@
+package com.baeldung.socket;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+public class GreetServerTest {
+	@Test
+	public void givenGreetingClient_whenServerRespondsWhenStarted_thenCorrect() {
+		GreetClient client = new GreetClient();
+		client.startConnection("127.0.0.1", 6666);
+		String response = client.sendMessage("hello server");
+		assertEquals("hello client", response);
+	}
+
+}