#include <GUIConstantsEx.au3>
#include <MsgBoxConstants.au3>

; Start First clicking on "1. Server"
; Then start a second instance of the script selecting "2. Client"

Example()

Func Example()
        UDPStartup() ; Start the UDP service.

        ; Register OnAutoItExit to be called when the script is closed.
        OnAutoItExitRegister("OnAutoItExit")

        ; Assign Local variables the loopback IP Address and the Port.
        Local $sIPAddress = "127.0.0.1" ; This IP Address only works for testing on your own computer.
        Local $iPort = 65532 ; Port used for the connection.

        #Region GUI
        Local $sTitle = "UDP Start"
        Local $hGUI = GUICreate($sTitle, 250, 70)

        Local $idBtnServer = GUICtrlCreateButton("1. Server", 65, 10, 130, 22)

        Local $idBtnClient = GUICtrlCreateButton("2. Client", 65, 40, 130, 22)

        GUISetState(@SW_SHOW, $hGUI)

        While 1
                Switch GUIGetMsg()
                        Case $GUI_EVENT_CLOSE
                                ExitLoop
                        Case $idBtnServer
                                WinSetTitle($sTitle, "", "UDP Server started")
                                GUICtrlSetState($idBtnClient, $GUI_HIDE)
                                GUICtrlSetState($idBtnServer, $GUI_DISABLE)
                                If Not MyUDP_Server($sIPAddress, $iPort) Then ExitLoop
                        Case $idBtnClient
                                WinSetTitle($sTitle, "", "UDP Client started")
                                GUICtrlSetState($idBtnServer, $GUI_HIDE)
                                GUICtrlSetState($idBtnClient, $GUI_DISABLE)
                                If Not MyUDP_Client($sIPAddress, $iPort) Then ExitLoop
                EndSwitch

                Sleep(10)
        WEnd

        #EndRegion GUI
EndFunc   ;==>Example

Func MyUDP_Server($sIPAddress, $iPort)
        ; Assign a Local variable the socket and bind to the IP Address and Port specified.
        Local $iSocket = UDPBind($sIPAddress, $iPort)

        ; If an error occurred display the error code and return False.
        If @error Then
                ; Someone is probably already binded on this IP Address and Port (script already running?).
                Local $iError = @error
                MsgBox(($MB_ICONERROR + $MB_SYSTEMMODAL), "", "Server:" & @CRLF & "Could not bind, Error code: " & $iError)
                Return False
        EndIf

        ; Assign a Local variable to store the data received.
        Local $sReceived = ""

        Do
                ; We are waiting for the string "toto" OR "tata" (example script UDPSend): 4 bytes length.
                $sReceived = UDPRecv($iSocket, 4)
        Until $sReceived <> ""

        ; Notes: If you don't know how much length will be the data,
        ; use e.g: 2048 for maxlen parameter and call the function until the it returns nothing/error.

        ; Display the string received.
        MsgBox($MB_SYSTEMMODAL, "", "Server:" & @CRLF & "Received: " & $sReceived)

        ; Close the socket.
        UDPCloseSocket($iSocket)
EndFunc   ;==>MyUDP_Server

Func MyUDP_Client($sIPAddress, $iPort)
        ; Assign a Local variable the socket and connect to a listening socket with the IP Address and Port specified.
        Local $iSocket = UDPOpen($sIPAddress, $iPort)
        Local $iError = 0

        ; If an error occurred display the error code and return False.
        If @error Then
                ; The server is probably offline/port is not opened on the server.
                $iError = @error
                MsgBox(($MB_ICONERROR + $MB_SYSTEMMODAL), "", "Client:" & @CRLF & "Could not connect, Error code: " & $iError)
                Return False
        EndIf

        ; Send the string "toto" converted to binary to the server.
        UDPSend($iSocket, StringToBinary("toto"))

        ; If an error occurred display the error code and return False.
        If @error Then
                $iError = @error
                MsgBox(($MB_ICONERROR + $MB_SYSTEMMODAL), "", "Client:" & @CRLF & "Could not send the data, Error code: " & $iError)
                Return False
        EndIf

        ; Close the socket.
        UDPCloseSocket($iSocket)
EndFunc   ;==>MyUDP_Client

Func OnAutoItExit()
        UDPShutdown() ; Close the UDP service.
EndFunc   ;==>OnAutoItExit