Socket programming questions

- How you set client-server connection?
- What language?
- Using third-party Sockets libraries or the default libraries of the language?
- Provide information as much as you can.

I am using Java for this and I am using default libraries of the language

import java.io.*;
import java.net.*;
class Client
{
public static void main(String args[])throws IOException
{
Socket con=null;
PrintWriter out=null;
BufferedReader in=null;
try
{
con=new Socket("localhost",32);//Developed a socket connection by client
out=new PrintWriter(con.getOutputStream(),true);//Write user input to socket
in=new BufferedReader(new InputStreamReader(con.getInputStream()));//Retrieve input from socket
}
catch(UnknownHostException e)
{
System.err.println("Sorry host can't be found");
System.exit(1);
}
catch(IOException ef)
{
System.err.println("Sorry Input/output fails");
System.exit(1);
}
try
{
BufferedReader std=new BufferedReader(new InputStreamReader(System.in));
String inp;
while((inp=std.readLine())!=null)
{
out.println("User input:"+inp);//It will send user input to PrintWriter
System.out.println(in.readLine());
}
in.close();
std.close();
out.close();
con.close();
}
catch(Exception e)
{
System.out.println(e.getMessage());
}
}
}

For server side

import java.net.*;
import java.io.*;
class Server
{
public static void main(String args[])throws IOException
{
ServerSocket ss=null;
try
{
ss=new ServerSocket(4445);
}
catch(Exception e)
{
System.out.print("Sorry can't listen on port 4445");
System.exit(1);
}
Socket cs=null;
PrintWriter out=null;
BufferedReader in=null;
try
{
cs=ss.accept();
out=new PrintWriter(cs.getOutputStream(),true);
in=new BufferedReader(new InputStreamReader(cs.getInputStream()));
}
catch(Exception e)
{
System.out.println(e.getMessage());
System.exit(1);
}
try
{
BufferedReader std=new BufferedReader(new InputStreamReader(System.in));
String input,serve;
while((input=in.readLine())!="Bye")
{
System.out.println("Client says:"+input);
serve=std.readLine();
out.println(serve);
}
}
catch(Exception e)
{
System.out.println("second:"+e.getMessage());
}
}
}

The Program is successfull compiled but when i try execute client it simply refuses connection and I got the exception
connection refused connect
but when i try to execute this program in some one else computer it executes successfully

99.9% I am sure, if your code is working on 1 machine and not in your own machine then definitely the problem is with IP and port no. Are the port nos. you are using in your program free in your machine. Please confirm this.

Thanks and All the Best ! 😀

@goyal420 I tried your program in mymachine, in the starting I got error as following in "Client.java" program

init:
deps-jar:
compile-single:
run-single:
Sorry Input/output fails
Java Result: 1
BUILD SUCCESSFUL (total time: 1 second)

But now I replaced

ss=new ServerSocket(4445);

line in your Server.java with

ss=new ServerSocket(32);

, it worked like below

At server window

init:
deps-jar:
Compiling 1 source file to D:\Java Application\PRACTICE_JAVA\build\classes
compile-single:
run-single:
hi
Client says:User input:hi
hello
Client says:User input:yo !

At client window

init:
deps-jar:
compile-single:
run-single:
hi
hi
yo !
hello

Hope you got the point, if not please read once thoroughly about Socket Programming. I am sure, few articles are here on this forum itself. 😀

Thank you very much sookie for this..
Now my program is running successfully

GUys now i want to extend this program between two remote computers

i mean i want to establish connection between two via internet

Can you please explain me what changes i should made to my program for this?

I have also searched on google about this a lot but no satisfactory results

Come on Guys Please help me in this

I am badly stuck to this

How to establish communication between two computers via internet through socket programming?

Please help me

Change localhost to the remote machine IP.

I have already changed it but still it is not working

import java.net.*;
import java.io.*;
class Server
{
public static void main(String args[])throws IOException
{
ServerSocket ss=null;
InetAddress is=InetAddress.getLocalHost();
try
{
ss=new ServerSocket(8051,1,is);
}
catch(Exception e)
{
System.out.print(e.getMessage());
System.exit(1);
}
Socket cs=null;
PrintWriter out=null;
BufferedReader in=null;
try
{
cs=ss.accept();
out=new PrintWriter(cs.getOutputStream(),true);
in=new BufferedReader(new InputStreamReader(cs.getInputStream()));
}
catch(Exception e)
{
System.out.println(e.getMessage());
System.exit(1);
}
try
{
BufferedReader std=new BufferedReader(new InputStreamReader(System.in));
String input,serve;
while((input=in.readLine())!="Bye")
{
System.out.println("Client says:"+input);
serve=std.readLine();
out.println(serve);
}
}
catch(Exception e)
{
System.out.println("second:"+e.getMessage());
}
}
}

import java.io.*;
import java.net.*;
class Client
{
public static void main(String args[])throws IOException
{
Socket con=null;
PrintWriter out=null;
BufferedReader in=null;
//InetAddress is=null;
try
{
//is=InetAddress.getLocalHost();
con=new Socket("117.205.32.1",8051);//Developed a socket connection by client
out=new PrintWriter(con.getOutputStream(),true);//Write user input to socket
in=new BufferedReader(new InputStreamReader(con.getInputStream()));//Retrieve input from socket
}
catch(UnknownHostException e)
{
System.err.println("Sorry host can't be found");
System.exit(1);
}
catch(IOException ef)
{
System.err.println("Sorry Input/output fails");
System.exit(1);
}
try
{
BufferedReader std=new BufferedReader(new InputStreamReader(System.in));
String inp;
while((inp=std.readLine())!=null)
{
out.println("User input:"+inp);//It will send user input to PrintWriter
System.out.println(in.readLine());
}
in.close();
std.close();
out.close();
con.close();
}
catch(Exception e)
{
System.out.println(e.getMessage());
}
}
}

These are changes that i have made

Check firewall settings.

goyal420

Come on Guys Please help me in this

I am badly stuck to this

How to establish communication between two computers via internet through socket programming?

Please help me

What problem or exceptions you are getting with your current code?

no exception ,no errors at all

when i try to communicate with my friends through this ..
It doesn't work and shows me message "Sorry input/output fails"

I don't understand why?

May be due to wrong port no

But how can i find the port no suitable for this?

goyal420

no exception ,no errors at all

when i try to communicate with my friends through this ..
It doesn't work and shows me message "Sorry input/output fails"

I don't understand why?

May be due to wrong port no

But how can i find the port no suitable for this?

Hi, just now I tried running your code in my machine and my colleague's machine. It worked perfectly fine. Just please make sure
1. Both the machines are in network.
2. Server Program is running before making Client program to run.
3. The ip used in below statement of Client.java is of Server machine's ip.

con=

new Socket([IP of machine where Server.java is running],8051);//Developed a socket connection by client​

HEY have you Tried it through LAN or internet?

I had tried to make connection through internet .

goyal420

HEY have you Tried it through LAN or internet?

I had tried to make connection through internet .

LAN & internet should not matter. The only thing is both the machines should be in network. Tonight I will try it in internet also. Then will let you know.