Top Most TCP Client Server Core Java Program to send some data from client to server

Client can send some text to server server will respond with same text on server

First run Your Server Program with as below
java TCPEchoServer 80

Server Program as follows:

package com.myapp.socket;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.SocketAddress;

public class TCPEchoServer {
private static final int BUFSIZE = 32; // Size of receive buffer

public static void main(String[] args) throws IOException {
if (args.length != 1) // Test for correct # of args
throw new IllegalArgumentException("Parameter(s): <Port>");

int servPort = Integer.parseInt(args[0]);

// Create a server socket to accept client connection requests
ServerSocket servSock = new ServerSocket(servPort);

int recvMsgSize; // Size of received message
byte[] receiveBuf = new byte[BUFSIZE]; // Receive buffer

while (true) { // Run forever, accepting and servicing connections
Socket clntSock = servSock.accept(); // Get client connection

SocketAddress clientAddress = clntSock.getRemoteSocketAddress();
System.out.println("Handling client at " + clientAddress);

InputStream in = clntSock.getInputStream();
OutputStream out = clntSock.getOutputStream();

// Receive until client closes connection, indicated by -1 return
while ((recvMsgSize = in.read(receiveBuf)) != -1) {

out.write(receiveBuf, 0, recvMsgSize);
}
clntSock.close(); // Close the socket. We are done with this client!
}
/* NOT REACHED */
}
}

Now Client Program as Follows and run your client as below on command prompt

java TCPEchoClient localhost "hello world" 80

package com.myapp.socket;

import java.io.IOException;

import java.io.InputStream;

import java.io.OutputStream;

import java.net.Socket;

import java.net.SocketException;

public class TCPEchoClient {

public static void main(String[] args) throws Exception, IOException {

if ((args.length < 2) || (args.length > 3)) // Test for correct # of

// args

throw new IllegalArgumentException(

"Parameter(s): <Server> <Word> [<Port>]");

String server = args[0]; // Server name or IP address

// Convert argument String to bytes using the default character encoding

byte[] data = args[1].getBytes();

int servPort = (args.length == 3) ? Integer.parseInt(args[2]) : 7;

// Create socket that is connected to server on specified port

Socket socket = new Socket(server, servPort);

              // Socket class, which

     // creates a

            // stream-based network

// connection between a

// client and a server

/*

* If you are not familiar with hosts and ports, think of the host as a

* post office and the port as a post-office box. Just as a post office

* has many different post-office boxes, any host on the network can run

* many different servers at a time. Different servers use different

* ports for their addresses. To establish a connection, you must

* specify both the correct host and the correct port. Many services

* have standard default ports. Web servers run on port 80, POP email

* servers run on port 110, and so on

*/

System.out.println("Connected to server...sending echo string");

InputStream in = socket.getInputStream();

OutputStream out = socket.getOutputStream();

out.write(data); // Send the encoded string to the server

// Receive the same string back from the server

int totalBytesRcvd = 0; // Total bytes received so far

int bytesRcvd; // Bytes received in last read

while (totalBytesRcvd < data.length) {

if ((bytesRcvd = in.read(data, totalBytesRcvd, data.length

- totalBytesRcvd)) == -1)

throw new SocketException("Connection closed prematurely");

totalBytesRcvd += bytesRcvd;

} // data array is full

System.out.println("Received: " + new String(data));

socket.close(); // Close the socket and its streams

}

}