The datagram socket program terms client and server can be misleading. Two socket programs that have each bound a socket to a local address can send any number of datagrams to each other in any sequence. The program that sends the first data will act as a client. Any datagram sent to a destination address for which no program has bound a socket is lost. Care must be taken so that the program you intend to be the client does not begin sending datagrams until the server program has bound its socket to the destination address expected.

Typically, the structure for a datagram socket resembles the iterative server discussed in Designing an iterative server program.