Visual FoxPro

Check Whether a Socket Is Writable

Demonstrates Socket.CheckWriteable, which waits for the connected socket to become writable. It returns 1 if writable, 0 if it did not become writable before the timeout, or -1 on error.

Background. A maxWaitMs of 0 performs a nonblocking poll. This is useful for flow control before attempting a large send.

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Visual FoxPro

LOCAL lnSuccess
LOCAL loSocket
LOCAL lnBTls
LOCAL lnMaxWaitMs
LOCAL lnWritable

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

*  Wait up to 5 seconds for the socket to become writable.  Returns 1 if writable, 0 if it did not
*  become writable before the timeout, or -1 on error.
lnWritable = loSocket.CheckWriteable(5000)
IF (lnWritable < 0) THEN
    ? loSocket.LastErrorText
    RELEASE loSocket
    CANCEL
ENDIF

IF (lnWritable <> 1) THEN
    ? "The socket did not become writable before the timeout."
    RELEASE loSocket
    CANCEL
ENDIF

? "The socket is writable."

RELEASE loSocket