Difference between TCP and UDP sockets

Question

What is the difference between making a connection with TCP sockets (sock_stream) and UDP sockets (datagram). Up to now, I think like we can create a connection using connect function only for TCP sockets. But, it is possible for making a connection with UDP sockets. Up to now I didn't know about making a connection with UDP sockets. What is the difference between these two?

        int tcpsock = socket(AF_INET, SOCK_STREAM, 0);
        connect(tcpsock,(struct sockaddr*)&sa,sizeof(sa));

        int udpsock = socket(AF_INET, SOCK_DGRAM, 0);
        connect(udpsock,(struct sockaddr*)&sa,sizeof(sa));  // How ?

UDP is connectionless. so if we use UDP how it is possible to make a connection similar to TCP?

I already know about the difference between TCP and UDP. My doubt is, UDP is connectionless then how connect function returns success?

Have you tried typing "difference between TCP and UDP" into Google, and then reading some of the results? — Andrew
"Up to now, I think like we can create a connection using connect function only for tcp socket." Well, that's because the TCP protocol requires that. The UDP protocol is connectionless. — πάντα ῥεῖ
@πάνταῥεῖ But connect function returns 0(success) even for udp sockets. — mohangraj

user207421 user207421 · Accepted Answer · 2016-04-22T10:55:09

The connect() function in UDP (a) tells UDP where to send all datagrams, so you can use send() instead of sendto(), and (b) acts as a filter on incoming datagrams, so you can use recv() instead of recvfrom(). It doesn't do anything on the network: it's just a local operation. It always returns zero because it can't fail. However sending to a non-existent target can fail ...

It's all documented.

Difference between TCP and UDP sockets

1 Answers