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Intro: terminating a TCP connection

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• Terminating a TCP connection

  • Properties of the "disconnect" operation:

    Symmetric Both the client and server can initial (= perform) the disconnect (= "close") operation. (Unlike the TCP connection establishment --- which is always initiated by the client) Independent          Closing of one of the uni-directional TCP connection: have no effect of the other (uni-directional) TCP connection !!! In other words: It is possible for the client to close its TCP connection (to the server) without having the server to close its connection... (and vice versa)

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  • The Effect of closing of your own TCP connection:

    The client/server that closes its TCP connection: will no longer be able to transmit !!! The client/server that has closed its TCP connection: can still receive data from the server/client !!! (Recall that a TCP connection is uni-directional !!!!)

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• Programming note....
  • Network Programming Application Programming interfaces:

    "Sockets" (made pupolar by UC Berkeley) TLI (Transport Layer Interface) ---- (product by AT & T)

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  • Closing a TCP connection:

    The socket API does not support a one-sided close operation: when one end of a TCP "socket" is closed, then: the other end of the TCP "socket" is automatically closed by the socket API . The TLI API does support a one sided close operation: The function t_sndrel(int fd) will release the send (write) capability of the socket fd

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• Message used in the disconnection operation of TCP
  • FIN:

    FIN (sequence no) = terminiate the TCP connection Note: The FIN message is assigned with a sequence number The FIN message must be acknowledged !!!