[Gllug] sorts of ports

[Leigh Mason]

i'm having trouble visualising what's happening when people talk about
entering a machine via port x or port y, with regard to network
communication.

i understand that any i/o device has to have  interface circuits to
communicate data transfer to the cpu.
and that within each interface there are registers similar to the cpu and at
least one of those registers is a buffer register (for data) called a port.
(please correct me if i'm wrong).

when a connection is made between two computers there is only one interface
in action (modem for example)  that the data is being carried across. the
interface has a 16 bit data register allowing the 65535 possible port
numbers, but it is still just one physical port - right?

is it just the program, say a web browser,  that will constantly send a read
request to the modem port to check whether the data in the register is
addresses to it (contains 80 in the address) and if an ftp app is running it
also sends repeated read requests to the modem port to check it's data
contains a 21 in it's address or whatever ???

or am i barking up the wrong tree?

thanks, leigh









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