h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

I am developing an application who main form title keeps changing. How can I adapt the sendmessage api to account for this?

There are two possibilities....

First you can use FindWindow() to return the window handle if you know it's caption, or it's class name :

Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long

hwndRet = FindWindow("OpusApp",vbNullString)

will find the first MS Word window...

Or you can write your server application so that it responds to a particular message by returning it's window handle. Then when a client starts up they broadcats a "where are you" message which the server responds to with an "I am here" message.

Declare Function RegisterWindowMessage Lib "user32" Alias "RegisterWindowMessageA" (ByVal lpString As String) As Long

Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long,ByVal lParam As Long) As Long
Public Const HWND_BROADCAST = &HFFFF&

Call SendMessage(HWND_BROADCAST, RegisterWindowmessage("WM_WhereAreYou"), Me.hwnd, 0)

Then when the server recieves it....

If wMsg = RegisterWindowmessage("WM_WhereAreYou") Then
SendMessage(wParam, RegisterWindowMessage("WM_IAmHere"), Me.hwnd, 0)

Hope this helps,
Duncan