Systemd socket: listendatagram vs listenstream In this very nice presentation of `systemd` the first speaker presents two cases of socket-based service activation. The first unit file corresponds to a `tftp` socket and it is the following `tftp.socket` [Unit] Tftp server activation socket [Socket] ListenDatagram=69 [Install] WantedBy=sockets.target The second is the example of the also socket-activated `cockpit` service on RHEL7 `cockpit.socket` [Unit] Description=Cockpit Web Server Socket Documentation=man:cockpit-ws(8) [Socket] ListenStream=9090 [Install] WantedBy=sockets.target I assume that both values of `ListenDatagram` and `ListenStream` refer to the port each corresponding service will be activated by, what is the purpose of these 2 different namings?

See the systemd.socket man page. For internet sockets a simple number is indeed a port number and the difference between them is that datagram means udp and stream means tcp.

However, these options can also take values like `/my/file`, when they refer to Unix domain sockets, and the difference is as given in the link by Marko Kosmerl, namely whether a reader can see the boundaries between packets from a writer or not.