I'm trying to connect to a C# TCP server I'm running on EC2.
But my server's not responding. This is the code that running on the EC2:
static void Main(string[] args)
{
TcpListener serverSocket = new TcpListener(8888);
TcpClient clientSocket = default(TcpClient);
serverSocket.Start();
clientSocket = serverSocket.AcceptTcpClient();
Console.WriteLine("new client connected");
}
And them from my own PC I'm trying to run this code:
static void Main(string[] args)
{
TcpClient clientSocket = new TcpClient();
clientSocket.Connect("35.163.41.3", 8888);
Console.WriteLine("you connected to the server!");
}
This is the security group of my EC2:
What could the problem be?
It could be a number of things. First thing I would check is Windows Firewall on the server to make sure that it is allowing that port.
Related
I am trying to use a TcpListener. Every time I try to start the listener I get the error that the Address is already in use. I have looked at netstat and cant see anything on that endpoint(IP Address, Port).
class Program
{
static void Main(string[] args)
{
IPAddress ip = IPAddress.Parse("127.0.0.1");
TcpListener listener = new TcpListener(ip, 58000);
listener.Start();
}
}
When I run that I the error every time.
The error is pretty clear that another process (it's probably because of unfinisted exe of your program) bind the same port which you want to listen. Try to listen different port and see the case;
IPAddress ip = IPAddress.Parse("127.0.0.1");
TcpListener listener = new TcpListener(ip, 58001);
listener.Start();
Also, I strongly suggest you to use TcpView to inspect allocated ports.
You have for sure another process(most probably the same you are trying to run) running in background so you cannot open the port. Try to open and and ensure to close the connections:
public static void Main()
{
TcpListener server=null;
try
{
Int32 port = 58000;
IPAddress localAddr = IPAddress.Parse("127.0.0.1");
// TcpListener server = new TcpListener(port);
server = new TcpListener(localAddr, port);
// Start listening for client requests.
server.Start();
// DO ALL YOUR WORK
}
catch(SocketException e)
{
Console.WriteLine(e.ToString());
}
finally
{
// Stop listening for new clients.
server.Stop();
}
}
I need to use udp and tcp connections in my application,the TcpClient/TcpListener would rarely be active,but the udp one would be the main usage.
This is the server code:
static void Main(string[] args)
{
TcpListener listener = new TcpListener(IPAddress.Any, 25655);
listener.Start();
Socket sck = listener.AcceptTcpClient().Client;
UdpClient udpServer = new UdpClient(1100);
IPEndPoint remoteEP = new IPEndPoint(IPAddress.Any, 0);
var data = udpServer.Receive(ref remoteEP);
string result = Encoding.UTF8.GetString(data);
Console.WriteLine(result);
Console.Read();
}
And this is the Client:
static void Main(string[] args)
{
TcpClient client = new TcpClient("127.0.0.1", 25655);
Socket sck = client.Client;
UdpClient udpclient = new UdpClient();
IPEndPoint ep = new IPEndPoint(IPAddress.Parse("127.0.0.1"), 1100); // endpoint where server is listening
udpclient.Connect(ep);
byte[] data = UTF8Encoding.UTF8.GetBytes("Hello");
udpclient.Send(data,data.Length);
}
I'm establishing the Tcp connection at first,then i'm trying to connect and send data from the client to the server.
From a breakpoint i add, i can see that the Tcp part works properly,the client finishes the program but in the server,it's hangs on the receiving part var data = udpServer.Receive(ref remoteEP);
like no data arrived..when i remove the tcp code part(the first 2 lines from the server and the client) it works great,shows the result message.
Does anyone know why im unable to get the data from the client?
Thanks in advance.
The main difference between UDP and TCP is that TCP is going to try to resend the message until the server tells the client it has received it. UDP is going to send and forget it even if the packet never reach or the host doesn't exist at all
Here is the flow of your code
Server starts up TCP
Client sends TCP
Server Receives TCP
Client sends UDP (server did not listen yet, packet lost but UDP doesn't care)
Server starts to listen to UDP
Server waiting for UDP to come <--- hang
You would like to do some multithread programming and start both of them at the same time before you tries to send message from the client.
The thing is that listener.AcceptTcpClient() blocks your current thread and UdpClient on server side is not established before Tcp connection created. In fact, your server is waiting for Tcp connection and only after that starting listening of Udp connections, while your client creates 2 connections one by one. My suggestions is - your server starting listening Udp port after the moment client actually sent data. The easiest way to check my suggestions - for client code add Thread.Sleep(1000) before sending data via UDP. In order to make that working you probably need to modify your code not blocking main thread but separate Tcp and Udp in the way similar to this:
static void Main(string[] args)
{
Task.Factory.StartNew(() =>
{
TcpListener listener = new TcpListener(IPAddress.Any, 25655);
listener.Start();
Socket sck = listener.AcceptTcpClient().Client;
// ToDo: further actions related to TCP client
}, TaskCreationOptions.LongRunning);
UdpClient udpServer = new UdpClient(1100);
IPEndPoint remoteEP = new IPEndPoint(IPAddress.Any, 0);
var data = udpServer.Receive(ref remoteEP);
string result = Encoding.UTF8.GetString(data);
Console.WriteLine(result);
Console.Read();
}
client code can probably stay as it is for this example, but for real project I would recommend to separate that as well, as for sure you would like to get back some data from server via Tcp.
What if you first start the UDP client on server side and then establish the TCP connection between client and server?!
Server
static void Main(string[] args)
{
UdpClient udpServer = new UdpClient(1100);
IPEndPoint remoteEP = new IPEndPoint(IPAddress.Any, 0);
TcpListener listener = new TcpListener(IPAddress.Any, 25655);
listener.Start();
Socket sck = listener.AcceptTcpClient().Client;
var data = udpServer.Receive(ref remoteEP);
string result = Encoding.UTF8.GetString(data);
Console.WriteLine(result);
Console.Read();
}
Client
static void Main(string[] args)
{
TcpClient client = new TcpClient();
client.Connect("127.0.0.1", 25655);
UdpClient udpclient = new UdpClient();
IPEndPoint ep = new IPEndPoint(IPAddress.Parse("127.0.0.1"), 1100); // endpoint where server is listening
udpclient.Connect(ep);
byte[] data = UTF8Encoding.UTF8.GetBytes("Hello");
udpclient.Send(data, data.Length);
}
My friend runs a simple C# Console Application that starts a TcpListener on Port 8484. This is how it's being done:
public static void Listen()
{
Listener = new TcpListener(IPAddress.Any, 8484);
Listener.Start();
Listener.BeginAcceptSocket(new AsyncCallback(EndAccept), null);
}
public static void EndAccept(IAsyncResult IAR)
{
Console.WriteLine("Connection accepted on Port 8484.");
Socket socket = Listener.EndAcceptSocket(IAR);
Instance = new Client(socket);
Listener.Stop();
Listener = null;
}
I connect to him using:
public void Connect()
{
_socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
try
{
_socket.Connect(IP, Port);
Debug.WriteLine("Connected with server!");
}
catch (Exception ex)
{
Debug.WriteLine(TypeName + " [ERROR] Could not connect to server # {0}:{1}: {2}", IP, Port, ex.Message);
}
}
However, for some reason - he can't accept the connection, it says it doesn't respond. Port 8484 is 100% opened at his computer.
Why does this happen?
Use telnet to verify connectivity to the remote server. E.g. run the command "telnet ip_address port". If it successfully connects then you can reach the server. If telnet cannot connect then you cannot reach the server, likely due to a firewall issue.
Try disabling the firewall.1
1 - Helped user in chat to test for firewall problems, and it has not open. That has the problem
I'm writing an application that deals with a server and a client. I don't necessarily know how to get the server to handle multiple clients, this is where I'm having problems with. Right now the server side only handles one client.
So how can I handle multiple clients.
You can keep the TcpListener open and accept multiple connections. To handle multiple connections efficiently, you will need to multi-thread the server code.
static void Main(string[] args)
{
while (true)
{
Int32 port = 14000;
IPAddress local = IPAddress.Parse("127.0.0.1");
TcpListener serverSide = new TcpListener(local, port);
serverSide.Start();
Console.Write("Waiting for a connection with client... ");
TcpClient clientSide = serverSide.AcceptTcpClient();
Task.Factory.StartNew(HandleClient, clientSide);
}
}
static void HandleClient(object state)
{
TcpClient clientSide = state as TcpClient;
if (clientSide == null)
return;
Console.WriteLine("Connected with Client");
clientSide.Close();
}
Now you can do all of the processing you need to do in HandleClient while the main loop will continue to listen for additional connections.
I'm trying to build a simple Client-Server Application with the following codes:
//SERVER
IPAddress ipAd = IPAddress.Parse("192.163.10.101");
TcpListener myList = new TcpListener(ipAd, 8001);
myList.Start();
Console.WriteLine("The server is running at port 8001...");
Console.WriteLine("The local End point is :" + myList.LocalEndpoint);
Console.WriteLine("Waiting for a connection.....");
Socket s = myList.AcceptSocket();
Console.WriteLine("Connection accepted from " + s.RemoteEndPoint);
//CLIENT
TcpClient tcpclnt = new TcpClient();
Console.WriteLine("Connecting.....");
tcpclnt.Connect("192.163.10.101",8001);
Console.WriteLine("Connected");
this actually does what I need wherein the client can connect to the server. However, when I try to run multiple instances of the client to connect with the server, the server only accepts the first client to connect. Meaning there's like a one-to-one connection wherein only one client can connect with the client. However, what I need is to give the server the ability to accept connections from more than one client.
If anyone can point me a possible solution to this, I'll really be appreciative! Thanks!
You need to call AcceptSocket again to accept another socket.
A typical design would be to have to call BeginAcceptSocket and in the callback call EndAcceptSocket, dispatch the client processing to its own thread (or a worker thread using async methods) and then call BeginAcceptSocket again.
This fragment is untested but should be more or less right/ get you thinking in the right direction.
class Server
{
public Server()
{
TcpListener listener = null;
// init the listener
listener.BeginAcceptSocket((ar) => AcceptLoop(ar, listener),null);
}
public void HandleClientSocketRead(IAsyncResult ar, byte[] recvBuffer, Socket clientSocket)
{
int recvd = clientSocket.EndReceive(ar);
//do something with the data
clientSocket.BeginReceive(recvBuffer, 0, 1024, SocketFlags.None, (ar2) => HandleClientSocketRead(ar2, recvBuffer, clientSocket), null);
}
public void AcceptLoop(IAsyncResult ar, TcpListener listener)
{
Socket clientSocket = listener.EndAcceptSocket(ar); // note that this can throw
byte[] recvBuffer = new byte[1024];
clientSocket.BeginReceive(recvBuffer, 0, 1024, SocketFlags.None, (ar2) => HandleClientSocketRead(ar2, recvBuffer, clientSocket), null);
listener.BeginAcceptSocket((ar) => AcceptLoop(ar, listener), null);
}
}
If you are looking to write a server, a good design is to have a [server].exe and a [client].exe. The [server].exe, will of course accept and process all incoming connections, maintain the client sockets, and perform whatever actions you need. Below is a very basic example on writing a server to accept multiple client sockets, and store them in a List object. This, however, is not multithreaded so the code, does block.
[server].exe
//-----------------------------------------------------------------------------
// <copyright file="Program.cs" company="DCOM Productions">
// Copyright (c) DCOM Productions. All rights reserved.
// </copyright>
//-----------------------------------------------------------------------------
namespace MultiSocketServerExample {
using System;
using System.Net.Sockets;
using System.Net;
using System.Collections.Generic;
class Program {
static List<Socket> m_ConnectedClients = new List<Socket>();
static void Main(string[] args) {
Socket host = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
host.Bind(new IPEndPoint(IPAddress.Any, 9999));
host.Listen(1);
while (true) {
m_ConnectedClients.Add(host.Accept());
Console.WriteLine("A client connected.");
}
}
}
}
Then to work with your clients: (Again, very basic example)
m_ConnectedClients[0].Send(Encoding.ASCII.GetBytes("hello!");
Network programming with the Socket class is a lot easier in my opinion then using TcpListener and TcpClient. The reason I say this is that it is already a really good and easy to use implementation, and by using TcpListener and TcpClient where they create further abstraction, lessenes your ability to understand what is going on (in my opinion).