SocketClient.java - A Simple Client Socket Application

JDK Tutorials - Herong's Tutorial Examples

∟SocketClient.java - A Simple Client Socket Application

This section provides a tutorial example on how to write a network application, SocketClient.java, that creates a client socket, connects to a remote socket server, sends and receives text messages.

Instead of using the telnet program, we can use the following simple client socket application to communicate with ReverseEchoer:

/* SocketClient.java
 * Copyright (c) HerongYang.com. All Rights Reserved.
 */
import java.io.*;
import java.net.*;
public class SocketClient {
   public static void main(String[] args) {
      BufferedReader in = new BufferedReader(new InputStreamReader(
         System.in));
      PrintStream out = System.out;
      try {
         Socket c = new Socket("localhost",8888);
         printSocketInfo(c);
         BufferedWriter w = new BufferedWriter(new OutputStreamWriter(
            c.getOutputStream()));
         BufferedReader r = new BufferedReader(new InputStreamReader(
            c.getInputStream()));
         String m = null;
         while ((m=r.readLine())!= null) {
            out.println(m);
            m = in.readLine();
            w.write(m,0,m.length());
            w.newLine();
            w.flush();
         }
         w.close();
         r.close();
         c.close();
      } catch (IOException e) {
         System.err.println(e.toString());
      }
   }
   private static void printSocketInfo(Socket s) {
      System.out.println("Remote address = "
         +s.getInetAddress().toString());
      System.out.println("Remote port = "
         +s.getPort());
      System.out.println("Local socket address = "
         +s.getLocalSocketAddress().toString());
      System.out.println("Local address = "
         +s.getLocalAddress().toString());
      System.out.println("Local port = "
         +s.getLocalPort());
   }
}

Note that:

The constructor used to instantiate the socket also performs the functions of bind() and connect().

Now, run ReverseEchoer first, then run SocketClient in a separate command window. If you type in the same text as in the previous test, you will get the following output:

herong> java SocketClient.java

Remote address = localhost/127.0.0.1
Remote port = 8888
Local socket address = /127.0.0.1:1073
Local address = /127.0.0.1
Local port = 1073
Welcome to Reverse Echo Server. Please type in some words.
Fish, I love you and respect you very much.
.hcum yrev uoy tcepser dna uoy evol I ,hsiF
But I will kill you dead before this day ends.
.sdne yad siht erofeb daed uoy llik lliw I tuB
.