Another client cannot be connected to the Client A because of his firewall.
You can create two majors kinds of network:
Server-Client
Peer-to-Peer
But a client can save some data to the server and the server can send them to all the clients (you don't need a Peer-to-Peer network for allow the Client B to send some data to the Client A).
Example: The Client B send his map position to the server, the server send the data to all the clients, so the Client A is able to draw a character tileset at the position of the Client B.
For connect two PCs together, you need to forward a port from the modem of your server to the PC used as server, and open the port from the firewall of the PC used as server.
You can also take a look here Creating a Multiplayer game in python, I give an example where the clients was able to connect them together with IRC and play at a Tic-Tac-Toe game (so you didn't have to manage a server). I have add an example in Java at the end of this post.
A simple server example:
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Date;
public class Server
{
public static void main(String[] args) throws Exception
{
ServerSocket listener = new ServerSocket(4000);
String line;
try
{
while (true)
{
Socket socket = listener.accept();
BufferedReader readerChannel = new BufferedReader(new InputStreamReader(socket.getInputStream()));
BufferedWriter writerChannel = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));
try
{
writerChannel.write(new Date().toString() + "
");
writerChannel.flush();
while ((line = readerChannel.readLine()) != null)
{
System.out.println(line);
}
}
finally
{
socket.close();
}
}
}
finally
{
listener.close();
}
}
}
A simple client example:
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.Socket;
import java.util.Date;
public class Client
{
public static void main(String[] args) throws Exception
{
Socket socket = new Socket("127.0.0.1", 4000);
BufferedWriter writerChannel = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));
BufferedReader readerChannel = new BufferedReader(new InputStreamReader(socket.getInputStream()));
String line;
writerChannel.write(new Date().toString() + "
");
writerChannel.flush();
while ((line = readerChannel.readLine()) != null)
{
System.out.println(line);
}
}
}
Also take a look at:
import javax.net.ssl.SSLSocket;
import javax.net.ssl.SSLSocketFactory;
public class Client
{
public static void main(String[] args) throws Exception
{
SSLSocketFactory socketBuilder = (SSLSocketFactory) SSLSocketFactory.getDefault();
SSLSocket socket = (SSLSocket) socketBuilder.createSocket("127.0.0.1", 4000);
}
}
A simple IRC example:
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import javax.net.ssl.SSLSocket;
import javax.net.ssl.SSLSocketFactory;
public class Client
{
public static void main(String[] args) throws Exception
{
SSLSocketFactory socketBuilder = (SSLSocketFactory) SSLSocketFactory.getDefault();
SSLSocket socket = (SSLSocket) socketBuilder.createSocket("irc.freenode.net", 6697);
BufferedWriter writerChannel = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));
BufferedReader readerChannel = new BufferedReader(new InputStreamReader(socket.getInputStream()));
String line, computerName, nick, login, channel = "#bot", channelPassword = "";
long id = 1;
computerName = java.net.InetAddress.getLocalHost().getHostName();
nick = computerName + "_" + id;
login = computerName + "_" + id;
writerChannel.write("NICK " + nick + "
"); // Join IRC with a specific Nick
writerChannel.write("USER " + login + " 8 * :" + login + "
"); // Join IRC with a specific User
writerChannel.flush();
while ((line = readerChannel.readLine()) != null)
{
if (line.indexOf("004") != -1) // If connected
{
break;
}
else if (line.indexOf("433") != -1) // If Nick already in use
{
id++;
nick = computerName + "_" + id;
login = computerName + "_" + id;
writerChannel.write("NICK " + nick + "
");
writerChannel.write("USER " + login + " 8 * :" + login + "
");
writerChannel.flush();
}
}
writerChannel.write("JOIN " + channel + " " + channelPassword + "
"); // Join a channel
writerChannel.flush();
while ((line = readerChannel.readLine()) != null)
{
try
{
line = line.substring(line.indexOf("#"));
channel = line.substring(0, line.indexOf(" "));
if (line.toLowerCase().startsWith("ping")) // avoid ping time-out
{
writerChannel.write("PONG :" + line.substring(5) + "
");
writerChannel.flush();
}
else if (line.toLowerCase().contains("!ping"))
{
writerChannel.write("PRIVMSG " + channel + " :pong
");
writerChannel.flush();
}
else if (line.toLowerCase().contains("!join"))
{
String newChannel = line.substring(line.indexOf("!join") + 6);
int stringPosition;
if ((stringPosition = newChannel.indexOf(" ")) != -1)
{
String newPassword = newChannel.substring(stringPosition + 1);
newChannel = newChannel.substring(0, stringPosition);
writerChannel.write("JOIN " + newChannel + " " + newPassword + "
");
writerChannel.flush();
}
else
{
writerChannel.write("JOIN " + newChannel + "
");
writerChannel.flush();
}
}
else if (line.toLowerCase().contains("!leave"))
{
writerChannel.write("PART " + channel + "
");
writerChannel.flush();
}
else if (line.toLowerCase().contains("!quit"))
{
writerChannel.write("QUIT
");
writerChannel.flush();
System.exit(0);
}
}
catch (Exception e)
{
}
}
}
}
I cannot give you an example for a Peer-to-Peer network because I have never do it. This is really difficult and you have to do a lot of research on internet.
More informations:
Hint - I have already answer at some similar questions. Even if the programming language are sometime different, I give you the link, the logic is always the same so it can maybe help you:
