Address family not supported by protocol

Question

Following code is a socket programming sample for a TCP client.

But when I run this, connect() is returned as Address family not supported by protocol.

I have he

Answer 1

I seen this error during bind. Cause was of using localhost instead of IP:

./myprogram localhost:7777
*** exception! `bind' failed for `localhost:7777' (97, Address family not supported by protocol)

./myprogram 127.0.0.1:7777
OK! Listening...

In addition: this error happens on one Linux host and does not appear on another. I check and compare network settings on this machines (lo device, /etc/hosts, /etc/host.conf, etc) and not found essential difference