Using Winsock, Page 5
So far, we've created a program that sends messages. And a program that receives messages.
But the send program can't receive. And the receive program can't send.
Now, I may not be an Einstein but the world pretty much survives on two-way communication. And even though most introductions don't usually delve beyond the code we've explored so far, let's be honest ICQ wouldn't have a membership base of ninety million if you could only send messages one way.
So in order to implement this functionality, I've created a quick 'template' application that allows you to both send and receive. You can download that here go on, have a play around and see what you can do!
And for all the groovy guys and gals printing this article, here's a dump of the core code, complete with basic error handling. All objects, such as Text Boxes have been given 'English' names to make the code more readable:
Private Sub Form_Load()On Error GoTo PortErr' Listen out for any possible connection' requests or data, etc.Winsock1.LocalPort = 202Winsock1.Listen' This uses port 201. To work, this program' must be run on two separate computers' - otherwise there will be a conflict with' two programs trying to access port 201Exit Sub PortErr: MsgBox "Another program is using port 201. This " & _ "may be because you're running another copy " & _ "of this program on the same computer. " & _"Unfortunately, this only works over a real " & _"network, either an office setup or the Internet. " & _"When two computers try to 'listen in' to the same " & _"part of a computer, one of them receives an error. " & _"I am alas the unlucky soul. Sorry! Here's an idea " & _"though - alter my Form_Load source code, changing the " & _"LocalPort property to 202 instead of 201. This should " & _"allow you to test both programs on the same machine!", _ vbCritical EndEnd SubPrivate Sub cmdSendMessage_Click() If Winsock1.State = sckConnected Then ' If connected, just send the data Winsock1.SendData (txtOutgoingMessage.Text) Else If MsgBox("You are not connected. " & _ "Connect to " & txtAddress.Text & "?", _ vbYesNo + vbQuestion) = vbYes Then ' Connect to the remote machine Winsock1.Close Winsock1.RemotePort = 201 Winsock1.RemoteHost = txtAddress.Text Winsock1.Connect ' Wait until full connection is made Do Until Winsock1.State = sckConnected DoEvents: DoEvents: DoEvents: DoEvents If Winsock1.State = sckError Then MsgBox "Problem connecting!" Exit Sub End If Loop ' Send the data Winsock1.SendData (txtOutgoingMessage) Else Call MsgBox("OK - not connected!", vbInformation) End If End If End SubPrivate Sub Winsock1_ConnectionRequest(ByVal requestID As Long) ' Accept an incoming connection request If Winsock1.State <> sckClosed Then Winsock1.Close Winsock1.Accept requestIDEnd SubPrivate Sub Winsock1_DataArrival(ByVal bytesTotal As Long) ' Display incoming data Dim strIncoming As String Winsock1.GetData strIncoming txtIncomingMessage.Text = strIncoming End Sub