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Ports TCP and UDP etc

  • 05-06-2005 12:54am
    #1
    JackKelly
    Registered Users, Registered Users 2 Posts: 3,225 ✭✭✭


    ok, im going to be honest, i dont understand ports and port fowarding at all. Can some explain this to me. What ARE ports and why are they there? The general idea i get is that they are the "doors" where information flows in and out while uploading/downloading.Where do they reside!?Whats TCP and UDP? How do i open/close ports. Can any program use any port? Its all a mystery.


Comments

  • #2
    Shane O' Malley
    Registered Users, Registered Users 2 Posts: 1,375 ✭✭✭Shane O' Malley


    That is a big area but in a basic form:

    The operating system creates them and generally controlles them.
    They do not reside anywhere but are software bases rather than physical.
    Their basic function is to ensure different streams of data from the internet are not all using the same port (Door)

    EG That the web page that you were looking for is using one port and that the e-mail you wanted is using another.

    All ports can be used for any purpose except for a few which are reserved for particular functions.

    In order to open or close particular reports you need to access your firewall.

    Do you know what one you are using?


  • #3
    DannyMac
    Registered Users, Registered Users 2 Posts: 17 ✭DannyMac


    Hi TimAy

    As previously stated, ports are essentially doors that the operating system uses.

    Different applications use different ports. Internet Explorer typically uses port 80. FTP uses port 21. Email services use port 25.

    To see these ports being opened/closed, open up a command prompt, and type netstat -an.

    Then open up a web browser to some site, and then do an netstat -an again. You will see the port to that website being opened on port 80.


    Hope this helps


  • #4
    Hobbes
    Registered Users, Registered Users 2 Posts: 21,264 ✭✭✭✭Hobbes


    A port is like a link to another site via TCP/IP (the internet).

    A server would have a listening port. Basically a port would be open (eg. 80) and that would listen to connections. The client would open up a random port (high range) and tell that port to connect to port 80 on the server. This would then allow you to talk to that server and see your webpage (as an example).

    The difference between TCP/IP and UDP is that UDP doesn't guarantee that it will ever deliver the message only that it sends it. TCP/IP is required to deliver all the packets its sends. UDP would be used for broadcast type applications (eg. Push servers, movie streaming, MMORPGs).

    UDP has a low overhead if you don't need to guarantee that the client needs all the packets.


  • #5
    hamster
    Registered Users, Registered Users 2 Posts: 1,766 ✭✭✭hamster


    DannyMac wrote:
    Hi TimAy

    As previously stated, ports are essentially doors that the operating system uses.

    Different applications use different ports. Internet Explorer typically uses port 80. FTP uses port 21. Email services use port 25.

    To see these ports being opened/closed, open up a command prompt, and type netstat -an.

    Then open up a web browser to some site, and then do an netstat -an again. You will see the port to that website being opened on port 80.


    Hope this helps



    This is interesting.... here's what I got after looking. What can be gleamed here? For example...
    1) about the listening TCP?
    2) Why so many 127.0.0.1 (internal?) ports established?
    3) So many UDPs?

    Active Connections

    Proto Local Address Foreign Address State
    TCP 0.0.0.0:135 0.0.0.0:0 LISTENING
    TCP 0.0.0.0:445 0.0.0.0:0 LISTENING
    TCP 0.0.0.0:1027 0.0.0.0:0 LISTENING
    TCP 0.0.0.0:1038 0.0.0.0:0 LISTENING
    TCP 0.0.0.0:2869 0.0.0.0:0 LISTENING
    TCP 0.0.0.0:5800 0.0.0.0:0 LISTENING
    TCP 0.0.0.0:5900 0.0.0.0:0 LISTENING
    TCP 0.0.0.0:44334 0.0.0.0:0 LISTENING
    TCP 0.0.0.0:44501 0.0.0.0:0 LISTENING
    TCP 127.0.0.1:1025 127.0.0.1:44334 ESTABLISHED
    TCP 127.0.0.1:1027 127.0.0.1:1029 ESTABLISHED
    TCP 127.0.0.1:1029 127.0.0.1:1027 ESTABLISHED
    TCP 127.0.0.1:1031 0.0.0.0:0 LISTENING
    TCP 127.0.0.1:1036 127.0.0.1:44334 ESTABLISHED
    TCP 127.0.0.1:1038 127.0.0.1:1041 ESTABLISHED
    TCP 127.0.0.1:1041 127.0.0.1:1038 ESTABLISHED
    TCP 127.0.0.1:1394 127.0.0.1:1395 ESTABLISHED
    TCP 127.0.0.1:1395 127.0.0.1:1394 ESTABLISHED
    TCP 127.0.0.1:1645 127.0.0.1:1646 ESTABLISHED
    TCP 127.0.0.1:1646 127.0.0.1:1645 ESTABLISHED
    TCP 127.0.0.1:10025 0.0.0.0:0 LISTENING
    TCP 127.0.0.1:10110 0.0.0.0:0 LISTENING
    TCP 127.0.0.1:10110 127.0.0.1:1647 TIME_WAIT
    TCP 127.0.0.1:44334 127.0.0.1:1025 ESTABLISHED
    TCP 127.0.0.1:44334 127.0.0.1:1036 ESTABLISHED
    TCP 159.134.149.96:135 159.134.145.219:1205 ESTABLISHED
    TCP 159.134.149.96:1498 192.67.198.54:80 ESTABLISHED
    TCP 192.168.0.1:139 0.0.0.0:0 LISTENING
    TCP 192.168.0.1:139 192.168.0.116:2666 ESTABLISHED
    TCP [::]:135 [::]:0 LISTENING 0
    TCP [::]:2869 [::]:0 LISTENING 0
    UDP 0.0.0.0:445 *:*
    UDP 0.0.0.0:500 *:*
    UDP 0.0.0.0:1026 *:*
    UDP 0.0.0.0:1028 *:*
    UDP 0.0.0.0:1032 *:*
    UDP 0.0.0.0:1037 *:*
    UDP 0.0.0.0:1039 *:*
    UDP 0.0.0.0:1061 *:*
    UDP 0.0.0.0:1075 *:*
    UDP 0.0.0.0:1427 *:*
    UDP 0.0.0.0:1597 *:*
    UDP 0.0.0.0:4500 *:*
    UDP 0.0.0.0:44334 *:*
    UDP 127.0.0.1:123 *:*
    UDP 127.0.0.1:1033 *:*
    UDP 127.0.0.1:1900 *:*
    UDP 159.134.149.96:123 *:*
    UDP 159.134.149.96:1900 *:*
    UDP 192.168.0.1:53 *:*
    UDP 192.168.0.1:67 *:*
    UDP 192.168.0.1:68 *:*
    UDP 192.168.0.1:123 *:*
    UDP 192.168.0.1:137 *:*
    UDP 192.168.0.1:138 *:*
    UDP 192.168.0.1:1900 *:*


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