How do I find the port number assigned to a UDP client (in .net/C#)?

c# udp udpclient
Charley Rathkopf picture Charley Rathkopf · Aug 22, 2009 · Viewed 8.7k times · Source

If I create a socket using 

var socket = new UdpClient(0,AddressFamily.InterNetwork);

How do I then find the port of the socket?

I'm probably being daft, but I'm not having luck in MSDN/Google (probably because it is 4:42 on a Friday and the sun is shining).

Background:

What I want to do is find an open port, and then report to another process to forward messages to me on that port. There may be multiple clients, so I don't want to used a fixed port.

Thanks.

Answer

dtb picture dtb · Aug 22, 2009

UdpClient is a wrapper around the Socket class which exposes the endpoint it's bound to through the LocalEndPoint property. Since you're using an UDP/IP client it's an IPEndPoint which has the desired Port property:

int port = ((IPEndPoint)socket.Client.LocalEndPoint).Port;

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