how can a network programming solution be tested at home? - vb.net

Question

I have a program used for the online multi-playing of sudoku (don't ask). I have written the code devoted to setting up specific tcpclient connections between instances of the application but when I tried to test it using the local host (IP:127.0.0.1) I got the error message:
"no connection could be made because the target machine actively refused it"
just when trying to set-up the client. regardless, it uses the same port to listen as to send and so later on this method would run into trouble but i need to test my solution so i ask: what is the easiest way (time is a factor) to test a network program at home. i have access to the following:
1 computer with the database installed via xampp (database is necessary)
up to 2 other computers without the database (could maybe be installed)
thank you.
edit:
'sets the destination IP to the HostAddress
IP = sender.CurrentRow.Cells.Item("HostAddress").Value
'creates a new instance of a client for send and recieving streams
client = New TcpClient(IP, port)
this is how I initialise the client. it is in the sub that a datagridview cell is clicked and HostAddress contains the IP address of the host as a string. it is the second line where the exception happened.

Answer 1

You provided too little information to actually help you find a bug, but here is how you can try if a basic connection on localhost works on your PC. Create two console projects, one the client and one server and insert the following code:
Client
Imports System.Net.Sockets
Imports System.Net
Module Client
Sub Main()
Dim IP As IPAddress = IPAddress.Parse("127.0.0.1")
Console.WriteLine("Start server and then press any key to connect.")
Console.ReadKey()
Console.WriteLine("Connecting...")
Dim client As New Net.Sockets.TcpClient
client.Connect(IP, 6583)
Console.WriteLine("Connected!")
Console.ReadKey()
client.Close()
End Sub
End Module
Server
Imports System.Net.Sockets
Imports System.Net
Module Server
Sub Main()
Dim IP As IPAddress = IPAddress.Parse("127.0.0.1")
Dim server As New TcpListener(IP, 6583)
server.Start()
Console.WriteLine("Waiting for connection...")
While server.Pending = False
End While
Dim connectedclient As TcpClient = server.AcceptTcpClient
Console.WriteLine("Client connected. Nice.")
Console.ReadKey()
End Sub
End Module
Compile and start the projects. Once the server starts it starts listening on port 6583 on localhost. Start the client and press a key and you should see messages saying that the connection works.
If it does, you code is faulty. If it doesn't you should check your firewall settings and stuff like this.