How to use Socket API for creating Client-Server application in Java

In this example we make use of ServerSocketChannel and SocketChannel to create a simple Echo application where in the Server would print the data sent by the client.

also read:

• Java Tutorials
• Java EE Tutorials
• Design Patterns Tutorials
• Java File IO Tutorials

The code is explained with the required comments:

[code lang=”java”]
import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.util.Scanner;

/**
* This creates a server on a particular IP address and the port.
*
*/
public class ServerClass {

public static void main(String[] args) {

// Create a Server socket channel.
try (ServerSocketChannel serverSocket = ServerSocketChannel.open()) {

// Bind the server socket channel to the IP address and Port
serverSocket.bind(new InetSocketAddress("127.0.0.1", 6667));
System.out.println("Waiting for client connections");

while (true) {

//Wait and Accept the client socket connection.
try (SocketChannel socketChannel = serverSocket.accept()) {

//Printing the address of the client.
System.out.println("Obtained connection from: "+socketChannel.getRemoteAddress().toString());

//Creating a reader for reading the content on the socket input stream.
Scanner socketReader = new Scanner(socketChannel.socket().getInputStream());
while(socketReader.hasNext()){

//Reading the content of the socket input stream.
System.out.println(socketReader.nextLine());

}

} catch(IOException ex){
ex.printStackTrace();
}
}

} catch (IOException ex) {
ex.printStackTrace();
}
}

}
[/code]
and the client which connects to the server is:
[code lang=”java”]
import java.io.IOException;
import java.io.PrintWriter;
import java.net.InetSocketAddress;
import java.nio.channels.SocketChannel;

public class CilentClass {

public static void main(String[] args) {

//Create a client socket.
try(SocketChannel socketChannel = SocketChannel.open()){

//Bind the client socket to the server socket.
socketChannel.connect(new InetSocketAddress("127.0.0.1", 6667));

//Writing to the socket channel.
PrintWriter writer = new PrintWriter(socketChannel.socket().getOutputStream(), true);
writer.println("Client sending instruction 1");
writer.println("Client sending instruction 2");
writer.println("Client sending instruction 3");
writer.println("Client sending instruction 4");

}catch(IOException ex){
ex.printStackTrace();
}

}
}
[/code]