TCP and UDP

TCP (Transmission Control Protocol, Transmission Control Protocol) is a connection-oriented protocol, reliable, guaranteed correctness, sequential arrival, flow control, congestion management, retransmission mechanism, window mechanism, more requirements for system resources and time, and flow mode sock_stream.

Server-side: Socket, bind, listen, accept, send, recv;
Client: Socket, connect, send, recv.

20-FTP Data port  21-ftp control Port  22-ssh Port  23-telnet  25-smtp 53-dns 80-http  110-pop3  443 -https

UDP (User data Protocol, Subscriber Datagram Protocol) is a non-connected protocol, unreliable, may drop packets, not necessarily in order, structure simple, datagram mode sock_dgram.

Server-side: Socket, bind,, Recvfrom, SendTo;
Client: Socket, SendTo, recvfrom.

53-dns  67-dhcp send Port  68-dhcp receive Port  69-tftp  161-SNMP  

TCP and UDP