Thread: UDP client needs bind() ??

I've never really gave UDP sockets much thought by some once told me that UDP client needs to be bind()ed to a port before the application will be able to send a datagram packet, is it true, or could it be some weird windows implementation bug, since the MSDN says nothing like that about UDP clients...


Thank you.

No, you don't need to bind a socket before using sendto. If the socket is not already bound, sendto will perform an implicit bind (for TCP sockets this implicit bind is done on connect). It is generally recommended to let Windows do an implicit bind if one doesn't need a specific local port. This avoids the issue of conflicts with other programs. An explicit bind will also activate the Windows firewall.

Originally Posted by anonytmouse

An explicit bind will also activate the Windows firewall.

You mean when I use bind() it activates the windows FW? why? is there a way to avoid it?

why?

Because it's the firewall's job to block traffic. If a program explicitly binds to a specific port, then it is essentially acting as a server on that port, and thus it introduces a security risk.

is there a way to avoid it?

The only way to avoid it (short of disabling the firewall) is to only bind implicitly. That is, don't call the bind() function, and let Windows handle it for you.

... (short of disabling the firewall) ...

Oh, sorry miss understood the "activate FW"
I thought that Windows is capable of starting the FW even after it was disabled.