A port is a port is a port. If your local port 1 is receiving data, then no
application can send from port 1 on your machine, regardless of the port
they wish to send to.

However, almost all applications which use sockets/ports are able to
maintain multiple connections at the same time (e.g. mail servers ALL
receive on port 25, and can often have 100s of simultaneous connections from
different servers without a problem). Another process however, cannot use
this port.

e.g. If you configured windows RDP to use port 80, and then wanted to use
port 80 with IIS, IIS will be unable to bind to the port, as it is in use by
another application. RDP however, could have as many connections on port 80
as the protocol supports.

Clear as mud?
"Peter Eisenman" <psallach@landsend.com> wrote in message
news:436dfc5f$0$21941$9b4e6d93@newsread2.arcor-online.net...
> Assume we look an a certain port say, port number 1234.
>
> Are there TWO different ports 1234 - one for the outgoing direction and
> one for the incoming?
> Or is there only one port which can be used only in one direction at a
> certain time: either
> as incoming or outgoing?
>
> If the ladder would be true then an already established incoming
> connection on port 1234 would block
> any outgoing connection on the same port.
>
> Peter