In C#, how to check if a TCP port is available?

Question

In C# to use a TcpClient or generally to connect to a socket how can I first check if a certain port is free on my machine? more info: This is the code I use: ``` TcpClient c; //I want to check here if port is free. c = new TcpClient(ip, port); ```

Accepted Answer

Since you're using a `TcpClient`, that means you're checking open TCP ports. There are lots of good objects available in the System.Net.NetworkInformation namespace.

Use the `IPGlobalProperties` object to get to an array of `TcpConnectionInformation` objects, which you can then interrogate about endpoint IP and port.

```
 int port = 456; //<--- This is your value
 bool isAvailable = true;

// Evaluate current system tcp connections. This is the same information provided
 // by the netstat command line application, just in .Net strongly-typed object
 // form.  We will look through the list, and if our port we would like to use
 // in our TcpClient is occupied, we will set isAvailable to false.
 IPGlobalProperties ipGlobalProperties = IPGlobalProperties.GetIPGlobalProperties();
 TcpConnectionInformation[] tcpConnInfoArray = ipGlobalProperties.GetActiveTcpConnections();

foreach (TcpConnectionInformation tcpi in tcpConnInfoArray)
 {
   if (tcpi.LocalEndPoint.Port==port)
   {
     isAvailable = false;
     break;
   }
 }

// At this point, if isAvailable is true, we can proceed accordingly.
```

In C#, how to check if a TCP port is available?

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