How can I put a timeout on connect()?
Andrew Gierth (firstname.lastname@example.org) has outlined the
following procedure for using select() with connect(), which will
allow you to put a timeout on the connect() call:
First, create the socket and put it into non-blocking mode, then call
connect(). There are three possibilities:
o connect succeeds: the connection has been successfully made (this
usually only happens when connecting to the same machine)
o connect fails: obvious
o connect returns -1/EINPROGRESS. The connection attempt has begun,
but not yet completed.
If the connection succeeds:
o the socket will select() as writable (and will also select as
readable if data arrives)
If the connection fails:
o the socket will select as readable *and* writable, but either a
read or write will return the error code from the connection
attempt. Also, you can use getsockopt(SO_ERROR) to get the error
status - but be careful; some systems return the error code in the
result parameter of getsockopt(), but others (incorrectly) cause
the getsockopt call itself to fail with the stored value as the
Sample code that illustrates this can be found in the socket-faq
examples, in the file connect.c.