#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 $idBtn_Server = GUICtrlCreateButton("1. Server", 65, 10, 130, 22)

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

    GUISetState(@SW_SHOW, $hGUI)

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