Reputation: 56
Socket Programming c# / Client-Server communication
I am trying to make 2 programs (in console application) in .NET that communicate together through the web (the code is from a video that you can find below, I am just trying to make the code work before adapting it). Forgive me, I'm not an experienced programmer.
I have a server and a client, they work perfectly when I run both of them on my computer (locally). I can connect multiple clients to the server, send requests and get a response. I am facing the problem when i run the server on a computer and the client on an other one and I try to connect through the internet.
I can connect to the server but communication does not work, there is no data exchange when try to request time as an example. I think that the problem is mostly coming from the network itself than the code.
Here's the code for the server:
class Program
{
private static Socket _serverSocket;
private static readonly List<Socket> _clientSockets = new List<Socket>();
private const int _BUFFER_SIZE = 2048;
private const int _PORT = 50114;
private static readonly byte[] _buffer = new byte[_BUFFER_SIZE];
static void Main()
{
Console.Title = "Server";
SetupServer();
Console.ReadLine(); // When we press enter close everything
CloseAllSockets();
}
private static void SetupServer()
{
// IPAddress addip = GetBroadcastAddress();
Console.WriteLine("Setting up server...");
_serverSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
_serverSocket.Bind(new IPEndPoint(IPAddress.Any , _PORT));
_serverSocket.Listen(5);
_serverSocket.BeginAccept(AcceptCallback, null);
Console.WriteLine("Server setup complete");
}
/// <summary>
/// Close all connected client (we do not need to shutdown the server socket as its connections
/// are already closed with the clients)
/// </summary>
private static void CloseAllSockets()
{
foreach (Socket socket in _clientSockets)
{
socket.Shutdown(SocketShutdown.Both);
socket.Close();
}
_serverSocket.Close();
}
private static void AcceptCallback(IAsyncResult AR)
{
Socket socket;
try
{
socket = _serverSocket.EndAccept(AR);
}
catch (ObjectDisposedException) // I cannot seem to avoid this (on exit when properly closing sockets)
{
return;
}
_clientSockets.Add(socket);
socket.BeginReceive(_buffer, 0, _BUFFER_SIZE, SocketFlags.None, ReceiveCallback, socket);
Console.WriteLine("Client connected, waiting for request...");
_serverSocket.BeginAccept(AcceptCallback, null);
}
private static void ReceiveCallback(IAsyncResult AR)
{
Socket current = (Socket)AR.AsyncState;
int received;
try
{
received = current.EndReceive(AR);
}
catch (SocketException)
{
Console.WriteLine("Client forcefully disconnected");
current.Close(); // Dont shutdown because the socket may be disposed and its disconnected anyway
_clientSockets.Remove(current);
return;
}
byte[] recBuf = new byte[received];
Array.Copy(_buffer, recBuf, received);
string text = Encoding.ASCII.GetString(recBuf);
Console.WriteLine("Received Text: " + text);
if (text.ToLower() == "get time") // Client requested time
{
Console.WriteLine("Text is a get time request");
byte[] data = Encoding.ASCII.GetBytes(DateTime.Now.ToLongTimeString());
current.Send(data);
Console.WriteLine("Time sent to client");
}
else if (text.ToLower() == "exit") // Client wants to exit gracefully
{
// Always Shutdown before closing
current.Shutdown(SocketShutdown.Both);
current.Close();
_clientSockets.Remove(current);
Console.WriteLine("Client disconnected");
return;
}
else
{
Console.WriteLine("Text is an invalid request");
byte[] data = Encoding.ASCII.GetBytes("Invalid request");
current.Send(data);
Console.WriteLine("Warning Sent");
}
current.BeginReceive(_buffer, 0, _BUFFER_SIZE, SocketFlags.None, ReceiveCallback, current);
}
}
And here the client code:
class Program
{
private static readonly Socket _clientSocket = new Socket
(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
private const int _PORT = 50114;
static void Main()
{
Console.Title = "Client";
ConnectToServer();
RequestLoop();
Exit();
}
private static void ConnectToServer()
{
int attempts = 0;
while (!_clientSocket.Connected)
{
try
{
attempts++;
Console.WriteLine("Connection attempt " + attempts);
_clientSocket.Connect("IpAddr", _PORT);
}
catch (SocketException)
{
Console.Clear();
}
}
Console.Clear();
Console.WriteLine("Connected");
}
private static void RequestLoop()
{
Console.WriteLine(@"<Type ""exit"" to properly disconnect client>");
while (true)
{
SendRequest();
ReceiveResponse();
}
}
/// <summary>
/// Close socket and exit app
/// </summary>
private static void Exit()
{
SendString("exit"); // Tell the server we re exiting
_clientSocket.Shutdown(SocketShutdown.Both);
_clientSocket.Close();
Environment.Exit(0);
}
private static void SendRequest()
{
Console.Write("Send a request: ");
string request = Console.ReadLine();
SendString(request);
if (request.ToLower() == "exit")
{
Exit();
}
}
/// <summary>
/// Sends a string to the server with ASCII encoding
/// </summary>
private static void SendString(string text)
{
byte[] buffer = Encoding.ASCII.GetBytes(text);
_clientSocket.Send(buffer, 0, buffer.Length, SocketFlags.None);
}
private static void ReceiveResponse()
{
var buffer = new byte[2048];
int received = _clientSocket.Receive(buffer, SocketFlags.None);
if (received == 0) return;
var data = new byte[received];
Array.Copy(buffer, data, received);
string text = Encoding.ASCII.GetString(data);
Console.WriteLine(text);
}
}
static void Main()
{
Console.Title = "Client";
ConnectToServer();
RequestLoop();
Exit();
}
private static void ConnectToServer()
{
int attempts = 0;
while (!_clientSocket.Connected)
{
try
{
attempts++;
Console.WriteLine("Connection attempt " + attempts);
_clientSocket.Connect("IpAddr", _PORT);
}
catch (SocketException)
{
Console.Clear();
}
}
Console.Clear();
Console.WriteLine("Connected");
}
"IpAddr" is a placeholder for the public IP of the router.
This is the video my current code is based on: https://www.youtube.com/watch?v=xgLRe7QV6QI
I took the code directly from it (you can find the 2 code files on the site linked in description).
I run the server, it awaits for a connection. I then run the clients which tries to connect to the server. I connects and on the server it shows the successful connection. The client then sends a request like "get time" and the server is supposed to catch it and respond:
byte[] data = Encoding.ASCII.GetBytes(DateTime.Now.ToLongTimeString());
current.Send(data);
Back to network side:
Here is a list of all the things I have tried, that were the usual main causes of the problem after looking for a solution for about a full day:
I already have a static public IP for the router (so the public IP never changes). Even though, I created a dynamic dns on noip.com.
I gave a static lease to the computer the server runs on, so it has always the same local ip.
I created rules in the windows firewall to make sure the port I use is opened. I did this on both computers trying to communicate.
I forwarded the port on the router so it points to the local ip of the computer the server runs on. (I tried with a lot of different ports, no chance)
I tried activating the "DMZ" on the router but it's most likely not a solution
I tried to create a ASP.NET website which page returns a string, publish it with IIS 7.5 and set it up. Works on localhost but using the public ip like "xx.xxx.xxx.xx:PORT/default/index" I get an error. Yet it shows the website name in the error. Also, when using the local IP of the computer, it doesn't work either (something like 192.168.1.180).
Thanks for you help.
Upvotes: 1
Views: 2921
Answers (1)
Reputation: 56
I learned about message framing, Thank you CodeCaster.
For people who are curious about it, here is an interesting link i found about it: http://blog.stephencleary.com/2009/04/message-framing.html
But before trying to change the code, I ran the server on an AWS vps and it worked instantly, the problem was probably comming from my isp or my router. I am just wondering how can it work without handling message framing.
Upvotes: 1