how to write nonblocking socket calls??

i had to open both comport and udp socket simultaneously.

roughly code is like this


Csocket sock;
sock.Create(sock_dgram.....................); //udp sock creation


if(flag==com_success)
read(com_port,.............................) //read 4rom com port

else
Receive From(buffer address,buflen,senders_ip,seneders_port) //receive
from udp socket


but read n receive from APIS are blocking suggest non blocking call for
receiving from udp socket using MFC/vc++

until the calls return next statement in a program cant be executed is
my promblem understood ????????//pls respond..,.