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37.16 Datagrams

A datagram connection communicates with individual packets rather than streams of data. Each call to process-send sends one datagram packet (see Input to Processes), and each datagram received results in one call to the filter function.

The datagram connection doesn't have to talk with the same remote peer all the time. It has a remote peer address which specifies where to send datagrams to. Each time an incoming datagram is passed to the filter function, the peer address is set to the address that datagram came from; that way, if the filter function sends a datagram, it will go back to that place. You can specify the remote peer address when you create the datagram connection using the :remote keyword. You can change it later on by calling set-process-datagram-address.

— Function: process-datagram-address process

If process is a datagram connection or server, this function returns its remote peer address.

— Function: set-process-datagram-address process address

If process is a datagram connection or server, this function sets its remote peer address to address.