I'm working on a simple hello world TCP/IP client server app in C# and am unable to get my client to connect. Can anyone offer any additional troubleshooting steps? I'm starting to run out of ideas...
Here are the relevant sections of code:
server:
Console.Out.WriteLine("About to bind address");
IPAddress ipAd = IPAddress.Parse("127.0.0.1");
Console.Out.WriteLine("Choose a port to bind...");
String port = Console.In.ReadLine();
int iPort = Int32.Parse(port);
TcpListener myList = new TcpListener(ipAd, iPort);
myList.Start();
Console.WriteLine("The server is running at: "+myList.LocalEndpoint);
Console.WriteLine("Waiting for a connection.....");
Socket s = myList.AcceptSocket();
Console.WriteLine("Connection accepted from " + s.RemoteEndPoint);
client:
Console.Out.WriteLine("enter address: ");
string address = Console.In.ReadLine();
Console.Out.WriteLine("enter port: ");
int port = Convert.ToInt32(Console.In.ReadLine());
TcpClient tcpclnt = new TcpClient();
Console.WriteLine("Connecting.....");
Console.Out.WriteLine("Address: " + address + ":" + port);
tcpclnt.Connect(address, port);
I am able to ping the server from the client machine, however I am unable to telnet to the server using the bound port. I've tried a variety of ports (a few in the low 8000s and a few up around 40000). I have disable windows firewall on both systems. The systems are connected to a router which is not on the internet. I've tried with and without port forwarding set to forward incoming requests on the given port to the server machine with no effect.
The only exception that I've been able to trap is thrown by the client:
No connection could be made because
the target machine actively refuses
it.
I checked for an InnerException but it seems that there are none - that is the base exception. Could that be right?
Not sure what else I should be looking at - any additional troubleshooting steps would be helpful.
Thanks!
I've run into this before. The trick is to bind to 0.0.0.0 rather than 127.0.0.1. When you bind to 127.0.0.1 the server will only accept connections from localhost. Binding to 0.0.0.0 it will accept all requests.
You also may want to nmap the host machine from the client and see what ports it sees as being open.
EDIT: If you hard code the IP address of the machine in it the listener will only listen on that network interface. If you use 0.0.0.0 the listener will listen on all available network interfaces. This includes interfaces between your computer and a USB attached hand held device, a second network card or a VPN link.
The code above is listening to request coming from the loopback address. This will effectively only listen to connection on that network, and that network only includes your machine.
Have you tried listening to the address bound to the network from which the connection should be coming? On a local network it should be something like 192.168.x.x or 10.x.x.x
try netstat -al on your machine (the exact command line varies between Windows and unix) and see if the server is listening on the port
Why don't you use .NET remoting? It is better than doing a TCP/IP client server. You can pass messages between objects.
Have you tried running the client server on the same machine to make sure the connection is made first? Beyond that try using the router assigned or static IP of the machine running the server vs binding to loopback.
Related
I have a server and a client app, the server throws no exception and seems to listen properly but the clients aren't able to connect for some reasons, I tried with both local network and public IP.
-With local network's IP I can connect to it only when the client app is runned on the same computer than the server.
-With public IP nothing can connect to the server.
However in both cases when the connection fails, it behaves always the same : waits for aproximately 5-10 seconds and then throws System.Net.Socket.SocketException. I tried with port 1507 first then tried with port 80 but it didn't change anything
Server
IPAddress adress = IPAddress.Parse(MyIp);
TcpListener listener = new TcpListener(adress, 80);
listener.Start();
TcpClient Client = await listener.AcceptTcpClientAsync();
Client
TcpClient client = new TcpClient();
client.ConnectAsync(IPAddress.Parse(MyIp), 80).GetAwaiter().GetResult();
I don't understand where the problem comes from, is it coming from my code or not? If not the what could it be and how could I fix it?
Have you tried Telnet from outside network on specific port?
If you can't connect probably is router port redirection or access is blocked by firewall.
I built tcp client/server application for my organisation. The server opens and listens to a specific port, and each client establishes Tcp Connection to the server port. Nothing special. The application works beautifully. But today, one client wanted the Tcp client app to work over WiFi network with firewall. The WiFi firewall is configured to block all ports by default. If I want my application to work, I have to give their network administrator a list of ports to open for my application. The server listening port is configurable so it is easy. Once I configure the port, I can give them is this specific port for the server. However the client app is unable to connect to the server because each time a TcpClient establishes a connection, it creates a random local Tcp port that will be blocked by their firewall.
Their network admin will not open all ports for the machine because they said it created security risks for their organisation. Therefore, I am looking for a way to force the client to open a specific local port when it establishes a Tcp connection. I've both looked into MSDN docs and been Googling but I haven't found an adequate answer. Would you be able to suggest a workaround or a third party library that can do that? Thank heaps.
I'm not aware of any way to have this level of control with TcpClient. However, if you manually create the Socket object, you can bind to a local port of your choosing:
var sock = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
// Specify the local port to use
var endpoint = new IPEndPoint(IPAddress.Any, 9999);
sock.Bind(endpoint);
// And connect to the remote end point
sock.Connect("example.com", 80);
Of course, by doing this you limit yourself to one connection on the machine.
how about use bind() like this(if you are using c++)
struct sockaddr_in cli;
memset(&cli, 0x00, sizeof(cli));
cli.sin_family = AF_INET;
cli.sin_port = htons(YOUR PORT);
cli.sin_addr.s_addr = inet_addr(YOUR IP ADDRESS);
int on = 1;
if (setsockopt(hSocket, SOL_SOCKET, SO_REUSEADDR, (char *)&on, sizeof(on)) < 0){
perror("Set Error");
}
bind(hSocket, (struct sockaddr *)&cli, sizeof(struct sockaddr));
int nRet = connect(hSocket,(sockaddr*)&svr, sizeof(svr));
I have been trying to do this for a while. I'm using the MSDN example for the TCPListener, being able to connect to it within the same newtork (i.e: from a terminal on my mobile phone).
I also understand that this works because of them being connected to the same router; I have entered to my router configurations and forwarded port 13450, which is the port I'm using on my TCP Listener constructor, to my computer's IP Address, and I've also submitted Windows firewall rules to not block this port for any external application.
After saving the port forwarding, I change IP Address on my C# Console Application to my router's IP (Default Gateway)
I've tried from hyperterminal on windows or from a terminal on my mobile phone to connect to my application (Using my router's IP and the corresponding port), but have never been able to manage this.
I would really appreciate help for this, as I cannot encounter a useful solution searching on Google
Thanks.
This is the code
Int32 port = 13450;
IPAddress localAddr = IPAddress.Parse("189.148.67.13");
// TcpListener server = new TcpListener(port);
server = new TcpListener(localAddr, port);
// Start listening for client requests.
server.Start();
// Buffer for reading data
Byte[] bytes = new Byte[256];
String data = null;
// Enter the listening loop.
while(true)
{
Console.Write("Waiting for a connection... ");
// Perform a blocking call to accept requests.
// You could also user server.AcceptSocket() here.
TcpClient client = server.AcceptTcpClient();
Console.WriteLine("Connected!");}
The IP is the public IP for my router; and on its config i've forwarded port 13450 to my local computer. Thanks
so I am currently programming a simple server/client to play some basic games i did in the past.
The problem is that I can only connect while I'm on the same computer, and not via LAN (as I would want it to work), here's the code I'm working with:
Server:
IPEndPoint Ep = new IPEndPoint(IPAddress.Any, 8000);
listener = new TcpListener(Ep);
listener.Start();
Client:
IPAddress direc = IPAddress.Parse(ipManager);
Ep = new IPEndPoint(direc, 8000);
The problem is that when I try connect from another computer (connected to the same Wi-Fi obviously) I get the following error:
A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond 192.168.0.5:8000
I shuold also add that this is the code when I try to connect:
Sever:
TcpClient client = listener.AcceptTcpClient();
Client:
client.Connect(Ep);
Apparently when I am connecting the server never "accepts" the connection, but I haven't been able to figure out why's that.
Since it works locally, you are probably using 127.0.0.1 or localhost as the server's listening interface. Try using 0.0.0.0 so it will listen on all interfaces or specify the IP address of the interface you want the server to listen on.
Try to connect to the port using telnet or netcat. Check if the port is accessible.
$ nc 192.168.0.5 8000
$ telnet 192.168.0.5 8000
I am using C# sockets to have a connection between a device (client) and a computer (server).
All is working good except for the fact that I am trying to avoid the user to enter the IP address and port number wherein to connect to on the device. Instead I want a listbox or drop down list of all IP addresses with listening sockets. Just wondering if there's a way to get all the IP addresses and port numbers of hosts with listening (socket)?
Thanks for any help! :)
What you're asking to do is called a port scan. It basically involves testing each IP address in a range and each port and reporting the success of that attempt. It's slow and it will cause a lot of alarms if there is any kind of threat monitoring on the network because port scanning is one of the ways attackers try to find network vulnerabilities.
So in short, this is a bad idea and probably won't be responsive enough for you to use for this purpose. Instead what you might consider is using a central server as a "directory" that each server would register with.
Or you can send out a broadcast on your subnet and wait for servers to respond. This is how some of the peer networking works in Windows for example. Note that this assumes you are the developer of the server as well and you can add in the logic necessary for the server to listen for broadcasts.
By using UDP broadcast, you can send out the data to the Server which are listening at the fixed port. The following is the working example.
foreach (IPAddress ip in allLocalNetworkAddresses.AddressList)
{
Socket client = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
//Allow sending broadcast messages
client.SetSocketOption(SocketOptionLevel.Socket,
SocketOptionName.Broadcast, 1);
//Create endpoint, broadcast.
IPEndPoint AllEndPoint = new IPEndPoint(IPAddress.Broadcast, Port);
byte[] sendData = Encoding.ASCII.GetBytes("1");
//Send message to everyone on this network
client.SendTo(sendData, AllEndPoint);
Console.Write("Client send '1' to " + AllEndPoint.ToString() +
Environment.NewLine);