Check if a port is open

Question

I can\'t seem to find anything that tells me if a port in my router is open or not. Is this even possible?

The code I have right now doesn\'t really seem to work...<

Answer 1

A better solution where you can even specify a timeout:

using System;
using System.Net.Sockets;

// ...

bool IsPortOpen(string host, int port, TimeSpan timeout)
{
    try
    {
        using(var client = new TcpClient())
        {
            var result = client.BeginConnect(host, port, null, null);
            var success = result.AsyncWaitHandle.WaitOne(timeout);
            client.EndConnect(result);
            return success;
        }
    }
    catch
    {
        return false;
    }
}

And, in F#:

open System
open System.Net.Sockets

let isPortOpen (host: string) (port: int) (timeout: TimeSpan): bool =
    try
        use client = new TcpClient()
        let result = client.BeginConnect(host, port, null, null)
        let success = result.AsyncWaitHandle.WaitOne timeout
        client.EndConnect result
        success
    with
    | _ -> false

let available = isPortOpen "stackoverflow.com" 80 (TimeSpan.FromSeconds 10.)
printf "Is stackoverflow available? %b" available