In C#, How to Check If a Tcp Port Is Available

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

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.

c# Checking whether a port is actively listening?

You can run netstat -na from command line to see all (including listening) ports.

If you add -b you will also see linked executable to each connection/listening.

In .NET you can get all listening connections with System.Net.NetworkInformation.IPGlobalProperties.GetIPGlobalProperties().GetActiveTcpListeners()

C#: How to find an available port in a range of specific ports in TCP?

I found a way to perform that:

private static int initialPort = 6001; // initial port to search from

public static void StartServerTCP()
{
    bool serverSet = false;
    while (!serverSet && initialPort <= 7000)
    {
        try
        {
            Console.WriteLine(Dns.GetHostName() + ": (Server:TCP) Trying to setup server at port: {0} [TCP]", initialPort);

            serverSocket.Bind(new IPEndPoint(GetIP(), initialPort));
            serverSocket.Listen(0);
            serverSocket.BeginAccept(AcceptCallback, null);
            Console.ForegroundColor = ConsoleColor.Yellow;
            Console.WriteLine(Dns.GetHostName() + ": (Server:TCP) Server setup completed at port {0} [TCP]\n", initialPort);
            Console.ForegroundColor = ConsoleColor.Gray;
            serverSet = true;
        }
        catch (Exception)
        {
            Console.WriteLine("\n" + Dns.GetHostName() + ": (Server:TCP) Port <{0}> is busy, trying a different one\n", initialPort);
            initialPort++;
        }
    }
}

How to check remote IP and Port is available?

Use the Ping class of .NET to find out if the system is up and connected, the use the PortScanner to check if the port is open. check these links for further reading and exploring.

http://msdn.microsoft.com/en-us/library/system.net.networkinformation.ping%28v=vs.110%29.aspx

http://social.msdn.microsoft.com/Forums/vstudio/en-US/8e4410bd-307f-4264-9575-cd9882653945/help-with-portscanner-in-c?forum=csharpgeneral

OR

public static bool PingHost(string hostUri, int portNumber)
{
    try
    {
        using (var client = new TcpClient(hostUri, portNumber))
            return true;
    }
    catch (SocketException ex)
    {
        MessageBox.Show("Error pinging host:'" + hostUri + ":" + portNumber.ToString() + "'");
        return false;
    }
}

Find the next TCP port in .NET

Here is what I was looking for:

static int FreeTcpPort()
{
  TcpListener l = new TcpListener(IPAddress.Loopback, 0);
  l.Start();
  int port = ((IPEndPoint)l.LocalEndpoint).Port;
  l.Stop();
  return port;
}

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