Dr. Mark Humphrys

School of Computing. Dublin City University.

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My big idea: Ancient Brain


CA114      CA170

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See book 6.2.1 and 6.5.2

Port - Logical (not physical) connection to computer (server).
One hardware link: Many ports.
One host (physical server) can run many services (listening processes) at different addresses.

IP address = Address of a host.
IP address + port = Address of a process (service) on a host.

List of ports.
1 to 65535 (16 bit no).

List of ports

Ports set aside for some "well-known" services:

Full list:

Server machine may run multiple server processes, each contactable on different port.
Conversely, multiple clients may want to contact same port (e.g. Web server).
Client creates socket at its end. Sends request to server (at port no). Server creates socket at its end dedicated to that client.
One port: Many sockets to that port.

ancientbrain.com      w2mind.org      humphrysfamilytree.com

On the Internet since 1987.

Wikipedia: Sometimes I link to Wikipedia. I have written something In defence of Wikipedia. It is often a useful starting point but you cannot trust it. Linking to it is like linking to a Google search. A starting point, not a destination. I automatically highlight in red all links to Wikipedia and Google search and other possibly-unreliable user-generated content.