sockets seems to not work on two computers - sockets

Question

i've faceing a weird problem i wrote a c# simple chat app and it works perfect when i launch the 2 clients on 1 machine but when i try one on my laptop(other computer but same ip) or send it to my friend it's just not working... we both turned off the firewall
thats the server code(part of it which i think can be the problem)
private void StartListening()
{
listener = new TcpListener(IPAddress.Any, listenport);
listener.Start();
while (true) {
try
{
Socket s = listener.AcceptSocket();
clientsocket = s;
clientservice = new Thread(new ThreadStart(ServiceClient));
clientservice.Start();
}
catch(Exception e)
{
Console.WriteLine(e.ToString() );
}
}
//listener.Stop();
}
and that's the client code
private void EstablishConnection()
{
statusBar1.Text = "Connecting to Server";
try
{
clientsocket = new TcpClient("10.0.0.3",serverport);
ns = clientsocket.GetStream();
sr = new StreamReader(ns);
connected = true;
}
catch (Exception e)
{
MessageBox.Show("Could not connect to Server","Error",
MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
statusBar1.Text = "Disconnected";
}
}
private void RegisterWithServer()
{
try
{
string command = "CONN|" + ChatOut.Text;
Byte[] outbytes = System.Text.Encoding.ASCII.GetBytes(command.ToCharArray());
ns.Write(outbytes,0,outbytes.Length);
string serverresponse = sr.ReadLine();
serverresponse.Trim();
string[] tokens = serverresponse.Split(new Char[]{'|'});
if(tokens[0] == "LIST")
{
statusBar1.Text = "Connected";
btnDisconnect.Enabled = true;
}
for(int n=1; n<tokens.Length-1; n++)
lbChatters.Items.Add(tokens[n].Trim(new char[]{'\r','\n'}));
this.Text = clientname + ": Connected to Chat Server";
}
catch (Exception e)
{
MessageBox.Show("Error Registering","Error",
MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
}
}
private void ReceiveChat()
{
bool keepalive = true;
while (keepalive)
{
try
{
Byte[] buffer = new Byte[2048];
ns.Read(buffer,0,buffer.Length);
string chatter = System.Text.Encoding.ASCII.GetString(buffer);
string[] tokens = chatter.Split(new Char[]{'|'});
if (tokens[0] == "CHAT")
{
rtbChatIn.AppendText(tokens[1]);
if(logging)
logwriter.WriteLine(tokens[1]);
}
if (tokens[0] == "PRIV") {
rtbChatIn.AppendText("Private from ");
rtbChatIn.AppendText(tokens[1].Trim() );
rtbChatIn.AppendText(tokens[2] + "\r\n");
if(logging){
logwriter.Write("Private from ");
logwriter.Write(tokens[1].Trim() );
logwriter.WriteLine(tokens[2] + "\r\n");
}
}
if (tokens[0] == "JOIN")
{
rtbChatIn.AppendText(tokens[1].Trim() );
rtbChatIn.AppendText(" has joined the Chat\r\n");
if(logging){
logwriter.WriteLine(tokens[1]+" has joined the Chat");
}
string newguy = tokens[1].Trim(new char[]{'\r','\n'});
lbChatters.Items.Add(newguy);
}
if (tokens[0] == "GONE")
{
rtbChatIn.AppendText(tokens[1].Trim() );
rtbChatIn.AppendText(" has left the Chat\r\n");
if(logging){
logwriter.WriteLine(tokens[1]+" has left the Chat");
}
lbChatters.Items.Remove(tokens[1].Trim(new char[]{'\r','\n'}));
}
if (tokens[0] == "QUIT")
{
ns.Close();
clientsocket.Close();
keepalive = false;
statusBar1.Text = "Server has stopped";
connected= false;
btnSend.Enabled = false;
btnDisconnect.Enabled = false;
}
}
catch(Exception e){}
}
}
private void QuitChat()
{
if(connected) {
try{
string command = "GONE|" + clientname;
Byte[] outbytes = System.Text.Encoding.ASCII.GetBytes(command.ToCharArray());
ns.Write(outbytes,0,outbytes.Length);
clientsocket.Close();
}
catch(Exception ex){
}
}
if(logging)
logwriter.Close();
if(receive != null && receive.IsAlive)
receive.Abort();
this.Text = "ChatClient";
}
private void StartStopLogging()
{
if(!logging){
if(!Directory.Exists("logs"))
Directory.CreateDirectory("logs");
string fname = "logs\\" + DateTime.Now.ToString("ddMMyyHHmm") + ".txt";
logwriter = new StreamWriter(new FileStream(fname, FileMode.OpenOrCreate,
FileAccess.Write));
logging = true;
btnLog.Text = "Stop Logging";
statusBar1.Text = "Connected - Log on";
}
else{
logwriter.Close();
logging = false;
btnLog.Text = "Start Logging";
statusBar1.Text = "Connected - Log off";
}
}
/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main(String[] args)
{
ChatClientForm cf = new ChatClientForm();
if(args.Length == 0)
cf.serveraddress = "localhost";
else
cf.serveraddress = args[0];
Application.Run(cf);
}
private void btnConnect_Click(object sender, System.EventArgs e)
{
if(ChatOut.Text == ""){
MessageBox.Show("Enter a name in the box before connecting","Error",
MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
return;
}
else
clientname = ChatOut.Text;
EstablishConnection();
if(connected)
{
RegisterWithServer();
receive = new Thread(new ThreadStart(ReceiveChat));
receive.Start();
btnSend.Enabled = true;
btnConnect.Enabled = false;
ChatOut.Text = "";
}
im breaking my head over 2 weeks with that... please someone help... :(

Answer 1

basically you have a device on your network (It is probably 10.0.01 or 10.0.0.254, but it could be something else). This is probably either your router / cablemodem / dsl modem. This allows you to do Network Address Translation / Port Address Translation (NAT/PAT). Which allows you to share 1 Public /WAN IP address (79.181.175.247) with all of the computers on your LAN (10.0.0.*). It does this by remapping all of your connections outbound to share the one address, and it keeps track of all of these connections. So when your computer goes out to connect to the internet (say browse a website). It connects from from 10.0.0.3 port 45356 to say google.com port 80. The firewall then maps the request to come from 79.181.175.247 port 5634 and sends the packet to google, and keeps track that return traffic to port 5634 maps to 10.0.0.3 port 45356, so it sends it back to the requesting host.
A side effect is that inbound connections don't know where to go. So for example if your serverport is 1234 on your chat program,and it is listening on 0.0.0.0 of your laptop (10.0.0.3). Your Firewall/Router (10.0.0.1?) doesn't know about this port (there are mechanisms, such as UPNP to communicate this up to compatible routers, but that is outside the scope of this). So you need to manually tell your router/firewall that any connections on the public IP address on port 1234 should be forwarded to port 1234 on your laptop. Depending upon the firewall/router this can have different names. Could be Port Forward, or could be called a mapping, etc... This is required so that the inbound traffic makes it directly to your program.
If you where to try this on your local lan (With firewalls disabled on your computer), you would need to use your internal IP addresses (10.0.0.x) to connect between laptop and other computer (you said same IP, but internally they need to have different addresses, or else they won't work).