TCP error when receiving data

SlowCoder74 · June 10, 2014

Server code:

Global $sTCPIPAddress = "127.0.0.1",$iTCPPort = "54321",$iTCPMaxConnections = 5
Global $iListenSocket = 0

Func _TCPServer_Initialize()
    OnAutoItExitRegister("OnAutoItExit")
    TCPStartup()

    ;initialize arrays to hold connection data
    Global $iTotalConnectedClients = 0
    Global $aTCPClientState[$iTCPMaxConnections],$aTCPClientSocket[$iTCPMaxConnections]
    Global $aTCPClientIP[$iTCPMaxConnections],$aTCPClientPort[$iTCPMaxConnections]
    Global $aTCPClientReceivedData[$iTCPMaxConnections]
    for $iConn = 0 to $iTCPMaxConnections - 1
        $aTCPClientState[$iConn] = ""
        $aTCPClientSocket[$iConn] = 0
        $aTCPClientIP[$iConn] = ""
        $aTCPClientPort[$iConn] = 0
        $aTCPClientReceivedData[$iConn] = ""
    next
EndFunc

Func _TCPServer_StartListen($sIPAddress,$iPort,$iMaxConnections = 10)
    ;open TCP port for listening
    $iSocket = TCPListen($sIPAddress, $iPort, $iMaxConnections)
    if @error Then return 0
    Return $iSocket
EndFunc

Func _TCPServer_StopListen($iListenSocket)
    ;stop listening for new connections
    TCPCloseSocket($iListenSocket)
EndFunc

Func _TCPServer_CheckForNewConnections($iListenSocket)
    ;check for any new connections
    Do
        $iNewSocket = TCPAccept($iListenSocket)
        if $iNewSocket <> -1 Then
            ;add to connection list
            for $iConn = 0 to $iTCPMaxConnections - 1
                if $aTCPClientState[$iConn] = "" Then
                    $aTCPClientState[$iConn] = "CONNECTED"
                    $aTCPClientSocket[$iConn] = $iNewSocket
                    $iTotalConnectedClients = $iTotalConnectedClients + 1
                    ExitLoop
                EndIf
            Next
        EndIf
    Until $iNewSocket = -1 or $iTotalConnectedClients = $iTCPMaxConnections
EndFunc

Func _TCPServer_ReceiveData($iClientSocket)
    ;retrieve any new data from all connected clients and add to each clients' data queue
    $iConn = _TCPServer_GetElemFromSocket($iClientSocket)
    if $aTCPClientState[$iConn] = "CONNECTED" Then
        local $sReceivedData = TCPRecv(Int($iClientSocket),128)
        if @error then
msgbox(0,"TCPServer - Receive Error",@error)
            _TCPServer_Disconnect($iClientSocket)
        Else
            if $sReceivedData <> "" Then $aTCPClientReceivedData[$iConn] = $aTCPClientReceivedData[$iConn] & $sReceivedData
        EndIf
    EndIf
EndFunc

Func _TCPServer_GetNextPacket($iClientSocket)
    ;parse client data queue and retrieve next packet
    $iConn = _TCPServer_GetElemFromSocket($iClientSocket)
    if StringInStr($aTCPClientReceivedData[$iConn],"[ENDPACKET]") > 0 Then
        Local $sPacket = StringLeft($aTCPClientReceivedData[$iConn],StringInStr($aTCPClientReceivedData[$iConn],"[ENDPACKET]") - 1)
        $aTCPClientReceivedData[$iConn] = StringRight($aTCPClientReceivedData[$iConn],StringLen($aTCPClientReceivedData[$iConn]) - (StringLen($sPacket + "[ENDPACKET]")))
        Return $sPacket
    EndIf
EndFunc

Func _TCPServer_Disconnect($iClientSocket = 0)
    ;disconnect client(s), and reset values
msgbox(0,"TCPServer","Disconnected")
    for $iConn = 0 to $iTCPMaxConnections - 1
        if $iClientSocket = 0 or $aTCPClientSocket[$iConn] = $iClientSocket Then
            TCPCloseSocket($iClientSocket)
            ;reset socket specific values
            if $aTCPClientSocket[$iConn] <> 0 then $iTotalConnectedClients = $iTotalConnectedClients - 1
            $aTCPClientState[$iConn] = ""
            $aTCPClientSocket[$iConn] = 0
            $aTCPClientIP[$iConn] = ""
            $aTCPClientPort[$iConn] = 0
            $aTCPClientReceivedData[$iConn] = ""
        EndIf
    next
EndFunc

Func OnAutoItExit()
    ;shut down TCP when application is closed
    _TCPServer_StopListen($iListenSocket)
    TCPShutdown()
EndFunc

Func _TCPServer_GetElemFromSocket($iClientSocket)
    ;return array element for given client socket
    for $iConn = 0 to $iTCPMaxConnections - 1
        if $aTCPClientSocket[$iConn] = $iClientSocket Then
            Return $iConn
        EndIf
    next
EndFunc


#include <EditConstants.au3>
#include <GUIConstantsEx.au3>
#include <WindowsConstants.au3>

_TCPServer_Initialize()
$iListenSocket = _TCPServer_StartListen($sTCPIPAddress,$iTCPPort)

#Region ### START Koda GUI section ### Form=
$Form1 = GUICreate("Form1", 256, 167, -1, -1)
$Input1 = GUICtrlCreateInput("Input1", 8, 8, 57, 21)
GUISetState(@SW_SHOW)
#EndRegion ### END Koda GUI section ###

While 1
    $nMsg = GUIGetMsg()
    Switch $nMsg
        Case $GUI_EVENT_CLOSE
            Exit
    EndSwitch

    ;check for new connections
    _TCPServer_CheckForNewConnections($iListenSocket)
    GUICtrlSetData($Input1,$iTotalConnectedClients)

    ;check for new received data
    for $iConn = 0 to $iTCPMaxConnections - 1
        if $aTCPClientState[$iConn] = "CONNECTED" Then _TCPServer_ReceiveData($aTCPClientSocket[$iConn])
    Next

    ;process new packets
    for $iConn = 0 to $iTCPMaxConnections - 1
        $sReceivedData = ""
        if $aTCPClientState[$iConn] = "CONNECTED" Then $sReceivedData = _TCPServer_GetNextPacket($aTCPClientSocket[$iConn])
        if $sReceivedData <> "" then
            msgbox(0,"",$sReceivedData)
        EndIf
    Next

    sleep(50)
WEnd

Client code:

Global $sTCPServerIPAddress = "127.0.0.1",$iTCPServerPort = "54321"
Global $iServerSocket = 0,$sConnState = ""





Func _TCPClient_Initialize()
    OnAutoItExitRegister("OnAutoItExit")
    TCPStartup()
EndFunc

Func _TCPClient_Connect($sIPAddress,$iPort)
    $iServerSocket = TCPConnect($sIPAddress,$iPort)
    if $iServerSocket <> -1 Then
        $sConnState = "CONNECTED"
        Return 1
    Else
        _TCPClient_Disconnect()
        Return 0
    EndIf
EndFunc

Func _TCPClient_Send($sDataToSend)
    if $sConnState = "CONNECTED" Then
        TCPSend($iServerSocket,$sDataToSend + "[ENDPACKET]")
        if @error Then _TCPClient_Disconnect()
    EndIf
EndFunc

Func _TCPClient_Disconnect()
    TCPCloseSocket($iServerSocket)
    $sConnState = ""
    $iServerSocket = 0
EndFunc

Func OnAutoItExit()
    _TCPClient_Disconnect()
    TCPShutdown()
EndFunc





#include <ButtonConstants.au3>
#include <GUIConstantsEx.au3>
#include <WindowsConstants.au3>

_TCPClient_Initialize()

#Region ### START Koda GUI section ### Form=
$Form1 = GUICreate("Form1", 238, 134, -1, -1)
$Button1 = GUICtrlCreateButton("Connect", 8, 8, 89, 25)
$Button2 = GUICtrlCreateButton("Disconnect", 8, 40, 89, 25)
$Input1 = GUICtrlCreateInput("Input1", 8, 72, 113, 21)
$Input2 = GUICtrlCreateInput("Input2", 8, 96, 105, 21)
$Button3 = GUICtrlCreateButton("Send", 120, 96, 49, 25)
GUISetState(@SW_SHOW)
#EndRegion ### END Koda GUI section ###

While 1
    $nMsg = GUIGetMsg()
    Switch $nMsg
        Case $GUI_EVENT_CLOSE
            Exit
        Case $Button1
            _TCPClient_Connect($sTCPServerIPAddress,$iTCPServerPort)
        case $Button2
            _TCPClient_Disconnect()
        case $Button3
            _TCPClient_Send(GUICtrlRead($Input2))
    EndSwitch

    GUICtrlSetData($Input1,$sConnState)

    sleep(50)
WEnd

These are quick/dirty TCP server/client code. I'm building the server to handle multiple simultaneous and continuous client connections.

When I run both of these together, netstat indicates the client is successfully connected to the server:

TCP    127.0.0.1:54321        0.0.0.0:0              LISTENING
TCP    127.0.0.1:54321        127.0.0.1:65519        ESTABLISHED

As soon as the server attempts to TCPRecv data from connected clients, it throws error and disconnects the client.

The error happens in the _TCPServer_ReceiveData function, line 56, when it attempts to TCPRecv.

I have verified that it appears to be using the correct and connected socket.

Before I shoot my computer, please tell me why the code is breaking?

ripdad · June 11, 2014

If you are using a newer version of AutoIt, try this as a temporary solution...

Func _TCPServer_ReceiveData($iClientSocket)
    ;retrieve any new data from all connected clients and add to each clients' data queue
    $iConn = _TCPServer_GetElemFromSocket($iClientSocket)
    If $aTCPClientState[$iConn] = "CONNECTED" Then
        Local $nError, $sReceivedData
        For $i = 1 To 100
            $sReceivedData &= TCPRecv(Int($iClientSocket), 128)
            $nError = @error
            If Not StringRegExp($nError, '(-1|0)') Then
                MsgBox(0, "TCPServer - Receive Error", $nError)
                _TCPServer_Disconnect($iClientSocket)
                ExitLoop
            ElseIf $sReceivedData <> "" Then
                $aTCPClientReceivedData[$iConn] = $aTCPClientReceivedData[$iConn] & $sReceivedData
                Exitloop
            EndIf
            Sleep(10)
        Next
    EndIf
EndFunc

If you continue to have an error, please reply what the error code is.

SlowCoder74 · June 11, 2014

I added your code. Had to modify the elseif part to move the ExitLoop statement to Else. Otherwise it was stuck in a loop. No biggie.

@error always returns -1, which, I guess is an unknown error. I found that just ignoring the -1 error seems to be the best method I've found.

This is the version of the _TCPServer_ReceiveData function that seems to work:

Func _TCPServer_ReceiveData($iClientSocket)
    ;retrieve any new data from all connected clients and add to each clients' data queue
    $iConn = _TCPServer_GetElemFromSocket($iClientSocket)
    If $aTCPClientState[$iConn] = "CONNECTED" Then
        Local $nError, $sReceivedData
        Do
            $sReceivedData = TCPRecv($iClientSocket, 128)
            $nError = @error
   Switch $nError
    Case 0 ;no error.  process normally
     if $sReceivedData <> "" Then
      $aTCPClientReceivedData[$iConn] = $aTCPClientReceivedData[$iConn] & $sReceivedData
      ;MsgBox(0,"TCPServer - Received",$sReceivedData)
     EndIf
    Case -1 ;unknown error?  doesn't seem to actually disconnect.  appears the error can just be ignored.
     ;MsgBox(0, "TCPServer - Receive Error - NULL", $nError)
     $sReceivedData = ""
    Case Else
     ;MsgBox(0, "TCPServer - Receive Error", $nError)
     _TCPServer_Disconnect($iClientSocket)
     $sReceivedData = ""
   EndSwitch
        Until $sReceivedData = ""
    EndIf
EndFunc

ripdad · June 11, 2014

As of v3.3.10.0:

-1 = no bytes have been received.

It's not an error. I have been talking to jpm about it here:

'?do=embed' frameborder='0' data-embedContent>>

The For loop 100 is my way of escaping the infinite, if something went wrong.

Works fine for me - although some might prefer something else.

SlowCoder74 · June 12, 2014

Ah, and that explains it. The help file is out of date, which only created confusion for me. I understand, as these guys are busy updating AutoIt, and sometimes things slip through the cracks.

Don't know why they set @error = -1 if there's no data. That seems to go against logic. Why not just keep @error = 0 and return ""? ... Unless they're trying to account for null or something?

I understand your finite looping. It would help mitigate a steady stream of data, and more or less equalize communications between clients.

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