TCP Echo implementation using Java

In the following program, we will demonstrate, how a connection can be established between client and server using Transport Layer Protocol - TCP. This code is self-explanatory. Hence, first, you will learn to develop server-side applications. Then, you will learn to develop client-side applications.

TcpEchoServer.java

package net.tcp.echo; import java.net.*; import java.io.*; public class TcpEchoServer { private static final int BUFSIZE = 32; public static void main(String[] args) throws IOException { int serverPort = 1000; ServerSocket serverSocket = new ServerSocket(serverPort); int recvMsgSize; byte[] receiveBuf = new byte[BUFSIZE]; while (true) { Socket clientSocket = serverSocket.accept(); SocketAddress clientAddress = clientSocket.getRemoteSocketAddress(); System.out.println("Client at " + clientAddress); InputStream in = clientSocket.getInputStream(); OutputStream out = clientSocket.getOutputStream(); while ((recvMsgSize = in.read(receiveBuf)) != -1) { System.out.println("Received Data : " + receiveBuf.toString()); out.write(receiveBuf, 0, recvMsgSize); } clientSocket.close(); } } }

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TcpEchoClient.java

package net.tcp.echo; import java.net.Socket; import java.net.SocketException; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; public class TcpEchoClient { public static void main(String[] args) throws IOException { if ((args.length < 2) || (args.length > 3)) throw new IllegalArgumentException("Parameter(s): <Server> [<Port>] <Word>"); String serverIP = args[0]; byte[] data = args[2].getBytes(); int serverPort = (args.length == 3) ? Integer.parseInt(args[1]) : 7; Socket socket = new Socket(serverIP, serverPort); System.out.println("Connected to server... sending echo message"); InputStream in = socket.getInputStream(); OutputStream out = socket.getOutputStream(); out.write(data); int totalBytesReceived = 0; int bytesRcvd; while (totalBytesReceived < data.length) { if ((bytesRcvd = in.read(data, totalBytesReceived, data.length - totalBytesReceived)) == -1) throw new SocketException("Connection closed prematurely"); totalBytesReceived += bytesRcvd; } System.out.println("Received: " + new String(data)); socket.close(); } }

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Happy Exploring!