Visual FoxPro

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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Visual FoxPro

LOCAL lnSuccess
LOCAL loSocket
LOCAL lnBTls
LOCAL lnMaxWaitMs
LOCAL lnMessageLength

lnSuccess = 0

loSocket = CreateObject('Chilkat.Socket')

*  Connect to the server using TLS.
lnBTls = 1
lnMaxWaitMs = 5000
lnSuccess = loSocket.Connect("example.com",5000,lnBTls,lnMaxWaitMs)
IF (lnSuccess = 0) THEN
    ? loSocket.LastErrorText
    RELEASE loSocket
    CANCEL
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.
lnMessageLength = loSocket.ReceiveCount()
IF (lnMessageLength < 0) THEN
    ? loSocket.LastErrorText
    RELEASE loSocket
    CANCEL
ENDIF

? "The peer will send " + STR(lnMessageLength) + " bytes."

RELEASE loSocket