The requested address is not valid in its context when I try to listen a port

Question

I am trying to connect to a sensor using network, the sensor's ip is 192.168.2.44 on port 3000;

My Code:

byte[] byteReadStream = null; // holds the data in byte buffer
IPEndPoint ipe = new IPEndPoint(IPAddress.Parse("192.168.2.44"), 3000);//listen on all local addresses and 8888 port
TcpListener tcpl = new TcpListener(ipe);
while (true)
{
    //infinite loop
    tcpl.Start(); // block application until data and connection
    TcpClient tcpc = tcpl.AcceptTcpClient();
    byteReadStream = new byte[tcpc.Available]; //allocate space
    tcpc.GetStream().Read(byteReadStream, 0, tcpc.Available);
    Console.WriteLine(Encoding.Default.GetString(byteReadStream) + "\n");
}

But when I run this code, I get this error:

The requested address is not valid in its context

Answer 1

Use IPAddress.Any to listen. This seems to be your goal:

//listen on all local addresses

The listening address you have specified is invalid for some reason. There is no need to specify a numeric address.

Answer 2

The TcpListener listens for connections from TCP network client, on a given port on your local machine. That is, for incoming connections. Your code will be acting as a "server" of sorts.

The requested address is not valid in its context

Simply, it means that the IP address given is not used by any network interface on your machine.

Use IPAddress.Any to listen on any IP address (i.e. network interface).

However, it might be the case that you need to connect to the sensor (on port 3000), not the other way around.

EDIT: The new exception just tells you that you have two applications trying to listen to the same interface/port combination. Do you have two instances running at the same time?

Answer 3

One of the reason for this issue could be the presence of defaultProxy section in the configuration file which would be routing every outgoing call via proxy address mentioned in this setting. Ensure that either there is a proxy server/service listening at the proxy address, or comment this section to stop the routing. In case the application configuration file does not have it, and this error is still there, check for the defaultProxy section in the machine.config file. machine.config should be available in folder C:\Windows\Microsoft.NET\Framework\v4.0.30319\Config. In our case it was the defaultProxy in machine.config.

Answer 4

Tech / Situation: I got this error while trying to run a Web API (ASP.Net Core 6) using my local IP so that I could connect to the API from a React Native App (maybe there's an easier way to do that).

Problem: I was at work, everything worked fine. I got home, and it gave the above error.

Realisation: Realised the router at work and at home generates (?) different local IP addresses (I don't know much about IPs and routers).

Solution:

1. Find your local IP
2. Copy Paste this and replace your localhost with it.