VB.NET: Check if a TCP Port on a remote site answers requests

check_client_tcp_port.vb

Imports System.Net.Sockets

Private Function _CheckTCPPort(ByVal sIPAdress As String, ByVal iPort As Integer, Optional ByVal iTimeout As Integer = 5000)
    Dim socket As New Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp)
    ' Connect using a timeout (default 5 seconds)
    Dim result As IAsyncResult = socket.BeginConnect(sIPAdress, iPort, Nothing, Nothing)
    Dim success As Boolean = result.AsyncWaitHandle.WaitOne(iTimeout, True)

    If Not success Then
        ' NOTE, MUST CLOSE THE SOCKET
        socket.Close()
        Return False
    End If
    Return True
End Function