Question

***Background****
I am new to TCP so I have question that may be a bit basic. I am trying to turn on O_NONBLOCK on a socket that is receiving data. Up until now I have tried to different ways to set O_NONBLOCK, itcl() and fcntl(). Right now I am trying to get fcntl() to work.

My Question: Are you supposed to set O_NONBLOCK before you connect the socket or after?

**my current implementation of fcntl() is based off off the link before the code:

How to reset a socket back to blocking mode (after I set it to nonblocking mode)?

//set socket to NONBlocking
on = fcntl(Socket,F_GETFL);
on = (on | O_NONBLOCK);
if(fcntl(Socket,F_SETFL,on) < 0)
    {
       perror("turning NONBLOCKING on failed\n");
    }

// DO CONNECT
rc = connect()

Thank you for taking the time to look at this

Answer 1

You are supposed to set O_NONBLOCK whenever you want. If you do it before connect, then connect will be non-blocking as well (returning EINPROGRESS; you can select or poll for writable state to wait for its completion).