How to receive UDP packages when using UdpClient class in C#
I am trying to write a graphical C# program that can communicate with my Node.js server.
I am using UdpClient class and I am able to send some messages to the server.
However, I don't know how to receive UDP packages from the server.
JavaScript and Windows Form Widgets are event-driven, but UdpClient class in C# doesn't have any convenient events related to data reception.
Also, I don't know where to put the code of package reception. Most of online examples are console program and my program is GUI based.
I want my program to continuously listen at a port and when a package comes in, the program can capture the package and display its content in a TextBox.
Any suggestions ?
You can listen to a port asynchronously using BeginReceive. It works in GUI applications too - just remember to send the data to the UI thread before interacting with the UI.
This example is from a WinForms application. I've put a multiline textbox on the form called txtLog.
private const int MyPort = 1337;
private UdpClient Client;
public Form1() {
InitializeComponent();
// Create the UdpClient and start listening.
Client = new UdpClient(MyPort);
Client.BeginReceive(DataReceived, null);
}
private void DataReceived(IAsyncResult ar) {
IPEndPoint ip = new IPEndPoint(IPAddress.Any, MyPort);
byte[] data;
try {
data = Client.EndReceive(ar, ref ip);
if (data.Length == 0)
return; // No more to receive
Client.BeginReceive(DataReceived, null);
} catch (ObjectDisposedException) {
return; // Connection closed
}
// Send the data to the UI thread
this.BeginInvoke((Action<IPEndPoint, string>)DataReceivedUI, ip, Encoding.UTF8.GetString(data));
}
private void DataReceivedUI(IPEndPoint endPoint, string data) {
txtLog.AppendText("[" + endPoint.ToString() + "] " + data + Environment.NewLine);
}