B4X

Wait for a Socket to Become Writable

Demonstrates Socket.SelectForWriting, which waits for the socket, or sockets in a socket set, to become writable. It returns 1 if writable, 0 on timeout, or -1 on error.

Background. A timeoutMs of 0 performs a nonblocking poll. This is useful before attempting to send when the peer may be applying flow control.

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B4X

Dim success As Boolean = False

Dim socket As ChilkatSocket
socket.Initialize("socket")

'  Connect to the server using TLS.
Dim bTls As Boolean = True
Dim maxWaitMs As Int = 5000
success = socket.Connect("example.com", 5000, bTls, maxWaitMs)
If success = False Then
    Log(socket.LastErrorText)
    Return
End If


'  Wait up to 5 seconds for the socket (or sockets in a socket set) to become writable.  Returns 1 if
'  writable, 0 on timeout, or -1 on error.
Dim ready As Int = socket.SelectForWriting(5000)
If ready < 0 Then
    Log(socket.LastErrorText)
    Return
End If

If ready <> 1 Then
    Log("The socket did not become writable before the timeout.")
    Return
End If

Log("The socket is ready for writing.")