java-socket communication

Socket client instance

The following GreetingClient is a client program that connects to the server via socket and sends a request, and then waits for a response.

// File name GreetingClient.java
 
import java.net.*;
import java.io.*;
 
public class GreetingClient
{
   public static void main(String [] args)
   {
      String serverName = args[0];
      int port = Integer.parseInt(args[1]);
      try
      {
         System.out.println( "Connect to host: " + serverName + ", port number: " + port);
         Socket client = new Socket(serverName, port);
         System.out.println( "Remote host address: " + client.getRemoteSocketAddress());
         OutputStream outToServer = client.getOutputStream();
         DataOutputStream out = new DataOutputStream(outToServer);
 
         out.writeUTF("Hello from " + client.getLocalSocketAddress());
         InputStream inFromServer = client.getInputStream();
         DataInputStream in = new DataInputStream(inFromServer);
         System.out.println( "Server response: " + in.readUTF());
         client.close();
      }catch(IOException e)
      {
         e.printStackTrace ();
      }
   }
}

 

Socket server instance

The following GreetingServer program is a server-side application that uses Socket to listen on a specified port.

// File name GreetingServer.java
 
import java.net.*;
import java.io.*;
 
public class GreetingServer extends Thread
{
   private ServerSocket serverSocket;
   
   public GreetingServer(int port) throws IOException
   {
      serverSocket = new ServerSocket(port);
      serverSocket.setSoTimeout(10000);
   }
 
   public void run()
   {
      while(true)
      {
         try
         {
            System.out.println( "Waiting for a remote connection, the port number is: " + serverSocket.getLocalPort() + "..." );
            Socket server = serverSocket.accept();
            System.out.println( "Remote host address: " + server.getRemoteSocketAddress());
            DataInputStream in = new DataInputStream(server.getInputStream());
            System.out.println(in.readUTF());
            DataOutputStream out = new DataOutputStream(server.getOutputStream());
            out.writeUTF( "Thank you for connecting me:" + server.getLocalSocketAddress() + "\nGoodbye!" );
            server.close();
         }catch(SocketTimeoutException s)
         {
            System.out.println("Socket timed out!");
            break;
         }catch(IOException e)
         {
            e.printStackTrace ();
            break;
         }
      }
   }
   public static void main(String [] args)
   {
      int port = Integer.parseInt(args[0]);
      try
      {
         Thread t = new GreetingServer(port);
         t.run();
      }catch(IOException e)
      {
         e.printStackTrace ();
      }
   }
}