UDP中的套接字需要文件描述符

Question

In my tcp program i have an int called fd, fd is set = to the file descriptor returned when accept() is called. I now want to make this code be udp instead of tcp, but udp has no accept() so how do i get the value accept() would have returned, but in udp?

Answer 1

UDP is connectionless, so listen() and accept() are not used (and connect() merely assigns a static binding so send() / recv() can be used instead of sendto() / recvfrom() , thus allowing the OS perform some filtering of packets for you). You get a UDP descriptor from socket() and then send/receive on it as needed, where sendto() (or connect() + send() ) tells it where to send an outbound packet to, and recvfrom() (or connect() + recv() ) tells you where an inbound packet came from. A single UDP socket can send packets to multiple clients using sendto() , and receive packets from multiple clients using recvfrom() .