accessing a server using socket connection

[preethi Ayyappan]

Hi,
I am very new to socket.I need to access a server using socket connection.Is it possible to do this?if so please give me a hint of code.

Thanks

[J radolf]

what type of code you want??

do you want a code where there is client-server interaction using Sockets?

[Swastik Dey]

Very much possible, at the Server side you use ServerSocket to crate a socket on particular port on which server will accept the request, you now create a Socket from this and wrap your IO streams to this.

  
ServerSocket server=new ServerSocket(1000); // server accepts requests on port 1000
Socket socket=server.accept();
//we now obain the IOStreams from socket
InputStream is=socket.getInputStream();
OutputStream os=socket.getOutputStream();
  

//Client creates a socket specifying the ip address and port number of server
Socket socket=new Socket("127.0.0.1",1000);
and obtains the IOStreams in the same way.

[preethi Ayyappan]

Thanks.I have tried the following sample:

   
import java.net.*;
import java.io.*;
public class JavaServer
{
public static void main(String h[])
{
try
{
Socket ss=new Socket("192.168.1.160",5038);
Socket s=ss.accept();
System.out.println("Client Accepted");
BufferedReader br=new BufferedReader(new
InputStreamReader(s.getInputStream()));
System.out.println(br.readLine());
PrintWriter wr=new PrintWriter(new
OutputStreamWriter(s.getOutputStream()),true);
wr.println("Welcome to Socket Programming");
}catch(Exception e){System.out.println(e);}
}
}
 

But i am getting the following error:

The method accept() is undefined for the type Socket

[Swastik Dey]

accept is a method of SeverSocket class not of socket class, so following should be your code at server end

 
   
import java.net.*;
import java.io.*;
public class JavaServer
{
public static void main(String h[])
{
try
{
ServerSocket server=new ServerSocket(5038);
Socket s=server.accept();
System.out.println("Client Accepted");
BufferedReader br=new BufferedReader(new
InputStreamReader(s.getInputStream()));
System.out.println(br.readLine());
PrintWriter wr=new PrintWriter(new
OutputStreamWriter(s.getOutputStream()),true);
wr.println("Welcome to Socket Programming");
}catch(Exception e){System.out.println(e);}
}
}
 
   

[J radolf]

/***Client Side Program***************/

 
package Test;

import java.io.*;
import java.net.*;
public class Requester{
	Socket requestSocket;
	ObjectOutputStream out;
 	ObjectInputStream in;
 	String message;
	Requester(){}
	void run()
	{
		try{
			//1. creating a socket to connect to the server
			requestSocket = new Socket("localhost", 2004);
			System.out.println("Connected to localhost in port 2005");
			//2. get Input and Output streams
			out = new ObjectOutputStream(requestSocket.getOutputStream());
			out.flush();
			in = new ObjectInputStream(requestSocket.getInputStream());
			//3: Communicating with the server
			do{
				try{
					message = (String)in.readObject();
					System.out.println("server>" + message);
					sendMessage("Hi my server");
					message = "bye";
					sendMessage(message);
				}
				catch(ClassNotFoundException classNot){
					System.err.println("data received in unknown format");
				}
			}while(!message.equals("bye"));
		}
		catch(UnknownHostException unknownHost){
			System.err.println("You are trying to connect to an unknown host!");
		}
		catch(IOException ioException){
			ioException.printStackTrace();
		}
		finally{
			//4: Closing connection
			try{
				in.close();
				out.close();
				requestSocket.close();
			}
			catch(IOException ioException){
				ioException.printStackTrace();
			}
		}
	}
	void sendMessage(String msg)
	{
		try{
			out.writeObject(msg);
			out.flush();
			System.out.println("client>" + msg);
		}
		catch(IOException ioException){
			ioException.printStackTrace();
		}
	}
	public static void main(String args[])
	{
		Requester client = new Requester();
		client.run();
	}
}
 

/**** Server Side Program****************/

 package Test;


import java.io.*;
import java.net.*;

public class Provider{
	
	ServerSocket providerSocket;
	Socket connection = null;
	ObjectOutputStream out; 
	ObjectInputStream in;
	String message;
	
	Provider(){}
	
	void run()
	{
		try{
			//1. creating a server socket
			providerSocket = new ServerSocket(2004, 10);
			//2. Wait for connection
			System.out.println("Waiting for connection");
			
			connection = providerSocket.accept();
			System.out.println("Connection received from " + connection.getInetAddress().getHostName());
			//3. get Input and Output streams
			out = new ObjectOutputStream(connection.getOutputStream());
			out.flush();
			in = new ObjectInputStream(connection.getInputStream());
			sendMessage("Connection successful");
			//4. The two parts communicate via the input and output streams
			do{
				try{
					message = (String)in.readObject();
					System.out.println("client>" + message);
					if (message.equals("bye"))
						sendMessage("bye");
				}
				catch(ClassNotFoundException classnot){
					System.err.println("Data received in unknown format");
				}
			}while(!message.equals("bye"));
		}
		catch(IOException ioException){
			ioException.printStackTrace();
		}
		finally{
			//4: Closing connection
			try{
				in.close();
				out.close();
				providerSocket.close();
			}
			catch(IOException ioException){
				ioException.printStackTrace();
			}
		}
	}
	void sendMessage(String msg)
	{
		try{
			out.writeObject(msg);
			out.flush();
			System.out.println("server>" + msg);
		}
		catch(IOException ioException){
			ioException.printStackTrace();
		}
	}
	public static void main(String args[])
	{
		Provider server = new Provider();
		while(true){
			server.run();
		}
	}
}
   

[J radolf]

Ya as Swastik said Its a method of ServerSocket class.

The code snippet i provided should work just try it once and post your queries here if you got any problems.

[preethi Ayyappan]

But i didnt get any output if i run this program.couldn't i mention the ip address with the port?

[J radolf]

Probably you should mention the IP address in the client side and mention only the port number in the server side using the ServerSocket class.

[Swastik Dey]

this is a simple client code

 
import java.net.*;
import java.io.*;
public class JavaClient
{
public static void main(String h[])
{
try
{
Socket s=new Socket("127.0.0.1",5038);
PrintWriter wr=new PrintWriter(new
OutputStreamWriter(s.getOutputStream()),true);
wr.println("Hi Server...");
wr.flush();
BufferedReader br=new BufferedReader(new
InputStreamReader(s.getInputStream()));
System.out.println(br.readLine());

}catch(Exception e){System.out.println(e);}
}
}
   

First execute the server code and from a different console execute the client code. The server console should display a method like Hi server and client console should display a message Welcome to Socket Programming.

[preethi Ayyappan]

swastik, I have tried your code.when running the server code,I am getting the following message:

java.net.BindException: Address already in use: JVM_Bind

And when running the client code,the output is:

Asterisk Call Manager/1.0

And can i run both the codes in eclipse in same system?

[Swastik Dey]

preethi
As from the error it seems that some other service is already running on that mentioned port, so just change the port number in the ServerSocket constructor, and accordingly make changes in the client code as well i.e. the port number, and make sure that server starts properly, then only client will run.

[Swastik Dey]

You should be able to run it in the same system, so either put the exact IP of the system in the client code, or use 127.0.0.1 i.e. the loopback address.

[Ulf Dittmer]

The code posted by preethi and Swastik is potentially buggy: Don't println to a Socket.

[J radolf]

what about my code sir?

[Swastik Dey]

Thanks, the information is really very useful, however while executing codes haven't faced any issues. But using print instead of println will of course optimize the code.

[Ulf Dittmer]

january radolf wrote:what about my code sir?

Does it use println in connection with a Socket?

[preethi Ayyappan]

Thanks ulf for correcting the error.

[Swastik Dey]

Was there any problem with port number too?

[preethi Ayyappan]

Hi,

All your codes help me to understand about sockets.I need to access the asterisk's commands using java socket.Is it possible to do this?

Thanks

[Ulf Dittmer]

I need to access the asterisk's commands using java socket.Is it possible to do this?

I would assume so; check the Asterisk documentation for details.