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  • port address explanation

    Please clarify what a port address is? I use specific port address for smtp and I see a different port address for my internet browsers. Is the port number I use for sending mail in my perl scripts dependent on the software application I am using?? For example if I use Cold Fusion to send mail I would use a Cold Fusion port number? But perl would use its own port number?

  • #2
    This would best be served/discussed in the Computer Hardware Forum.
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    • #3

      I'm sure someone will correct me if I'm wrong as I am still learning this myself but-

      Have a look here for a list of ports and the services \ applications that use them. Some ports are designated specifically for certain services. Any unassigned port above 1100 somthing (anyone?)can be used for anything you desire - ie. I use 7756 to force a port when playing Red Faction.

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      • #4
        that iana link is the best link you'll find....

        to quote my Cisco CCNA Semester 1 book....

        *digs it out*

        aherm.. here we go....

        Point-to-Point Protocol.....poison reverse update.....ah-ha! here it is: port.

        port: 1. An interface on an internetworking device (such as a router). 2. In IP terminology, an upper-layer process that receives information from lower layers. Ports are numbered, and many are associated with a specific process. For example, SMTP is associated with port 25. A port number of this type is called a well-known address. 3. To rewrite software or microcode so that it will run on a different hardware platform or in a different software environment than that for which it was originally designed.
        - Cisco Networking Academy Program: First-Year Companion Guide, Second Edition; page 939-940.

        Number 2 is what you're looking for. Ports 1024 - 4915....1? are "registered", 1 - 1023 are "well-known" and 49152 - 65535 are "available"

        One (slightly incorrect, but mostly right) way of thinking about it:

        Imagine your computer as an office building. Port numbers are the different floors. incoming mail is handled on floor 110, outgoing on floor 25, internet surfing on port 80. The upper floors are available on an "as needed" basis.

        That's one way.

        Another is to just think of each application on your computer has to have a door. Assign the door a number. Whenever another program (either on your computer or on another computer) want to talk to that program, they have to go through that door.

        To answer your question....it depends.

        When communication is established...there are 2 doors. An OUTGOING door, and an INCOMING door. Your application probably wants to know the "INCOMING" door (the port number of the service you're accessing). Operating systems have a nice tendency to just pick a free OUTGOING port to use to connect. Perhaps instead of OUTGOING and INCOMING, I should have used SOURCE and DESTINATION...... yes yes...swap all instances of OUTGOING with SOURCE and swap DESTINATION for INCOMING.... much better....


        • #5
          You can also look for a file called "services" which details all ports commonly used on a system. In linux it's "/etc/services" on windows it's usally %SYSTEM_ROOT%\etc\services" or something similar.
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          • #6


            open it with notepad