Simple chat server

Private WithEvents serverconn As foxtrot.xray.Announcer.Server

After defining our Server object, we will create a new instance of it. The server is a tad more complex in its initialization: it requires a service identifier, a port to use for listening to incoming connections, and a TTL for the service broadcast (this defines how many router boundaries your service broadcast will cross).

serverconn = New foxtrot.xray.Announcer.Server("ChatServer v1.0", 2000, 2)

Now, we add handlers for the ClientConnected and ClientDisconnected events, to add and remove users from the list when they connect or disconnect:

Private Sub serverconn_ClientConnected(ByVal client As _
  foxtrot.xray.Announcer.Server.ClientConnection) _
  Handles serverconn.ClientConnected
	' the ClientID property of the ClientConnection contains a string that
	' can be used as the unique ID of the Client
    AddClient(client.ClientID)
End Sub

Private Sub serverconn_ClientDisconnected(ByVal client _
  As foxtrot.xray.Announcer.Server.ClientConnection) _
  Handles serverconn.ClientDisconnected
	' the ClientID property used as a unique identifier
    RemoveClient(client.ClientID)
End Sub

Now, we add a handler for the DataReceived event, to handle all the messages coming from clients:

Private Sub serverconn_DataReceived(ByVal message As _
  foxtrot.xray.Announcer.Server.ClientMessage) _
  Handles serverconn.DataReceived
    Dim rdata As New Hashtable
    Dim sdata As New Hashtable
    Dim nick as string
    message.GetData(rdata)
    Dim connections() As foxtrot.xray.Announcer.Server.ClientConnection
    Select Case rdata("op")
        Case "nickset"
            ' look in the list of nicknames for requested nick
            ' If nick is found
                sdata("result") = "inuse"
            ' Else, this is a new nick
                sdata("result") = "ok"
                ' store the new nick in the list, and associate it to
                ' the ClientID property of the Client connection
            ' End If
            ' Send the reply
            message.Send(sdata)
        Case "chat"
			' Get the nickname associated with the ClientID of this
			' connection and store it in the nick variable      
            rdata("nick") = nick
            ' Get the list of Clients connected to this server
            connections = serverconn.Clients()
            ' Forward the chat text to all clients
            If Not (connections Is Nothing) Then
                For i As Integer = 0 To connections.Length - 1
                    connections(i).Send(rdata)
                Next
            End If
    End Select
End Sub

We have successfully implemented a networked application without using any actual networking code.