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  1. #1

    tcp connection alive time, port number reused and sequence number acqu

    I have some questions on TCP

    1 I think when a tcp connection is established between machine A and B, this connection will be always alive until there are RST or FIN packets or the tcp process is killed,
    so I can send packets from the client to the server serveral minutes or even several hours later after a TCP connection is established, as long as the sequence number and ack sequence number is correct, is it right?

    2 when a tcp connection is established, is it possible to check the current sequence number from kernel or program on the server side? if so, how to get it?
    Last edited by esolve; 03-20-2013 at 02:51 PM.

  2. #2
    TCP connections have a timeout setting for inactivity, and I think that's going to vary by settings on both machines and on any routers or firewalls between them. I think a typical timeout is two hours, but I've heard some programs or firewalls use as little as five minutes.

    I don't know how to check the sequence number. I looked at StackOverflow, and from that, it looks like if you use a packet sniffer like Wireshark you can capture all of the packets from the program and track the sequence number that way, but at least the people on Stack Overflow don't know of a way to capture that information on a running program without using a packet sniffer from the beginning.

    Good luck.

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