PureBasic

Receive a 4-byte Length Prefix from a Socket

Demonstrates Socket.ReceiveCount, which reads a four-byte length prefix as a signed 32-bit integer. A return value of -1 indicates failure.

Background. Reading the length prefix first tells the application exactly how many bytes to read for the message body, which is a reliable way to know when a full message has arrived.

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PureBasic

IncludeFile "CkSocket.pb"

Procedure ChilkatExample()

    success.i = 0

    socket.i = CkSocket::ckCreate()
    If socket.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    ;  Connect to the server using TLS.
    bTls.i = 1
    maxWaitMs.i = 5000
    success = CkSocket::ckConnect(socket,"example.com",5000,bTls,maxWaitMs)
    If success = 0
        Debug CkSocket::ckLastErrorText(socket)
        CkSocket::ckDispose(socket)
        ProcedureReturn
    EndIf

    ;  Read a four-byte length prefix as a signed 32-bit integer (network byte order by default).  A
    ;  return value of -1 indicates failure.
    messageLength.i = CkSocket::ckReceiveCount(socket)
    If messageLength < 0
        Debug CkSocket::ckLastErrorText(socket)
        CkSocket::ckDispose(socket)
        ProcedureReturn
    EndIf

    Debug "The peer will send " + Str(messageLength) + " bytes."


    CkSocket::ckDispose(socket)


    ProcedureReturn
EndProcedure