SEND Call

    CLOSED STATE (i.e., TCB does not exist)

      If the user does not have access to such a connection, then return
      "error:  connection illegal for this process".

      Otherwise, return "error:  connection does not exist".

    LISTEN STATE

      If the foreign socket is specified, then change the connection
      from passive to active, select an ISS.  Send a SYN segment, set
      SND.UNA to ISS, SND.NXT to ISS+1.  Enter SYN-SENT state.  Data
      associated with SEND may be sent with SYN segment or queued for
      transmission after entering ESTABLISHED state.  The urgent bit if
      requested in the command must be sent with the data segments sent
      as a result of this command.  If there is no room to queue the
      request, respond with "error:  insufficient resources".  If
      Foreign socket was not specified, then return "error:  foreign
      socket unspecified".

    SYN-SENT STATE
    SYN-RECEIVED STATE

      Queue the data for transmission after entering ESTABLISHED state.
      If no space to queue, respond with "error:  insufficient
      resources".

    ESTABLISHED STATE
    CLOSE-WAIT STATE

      Segmentize the buffer and send it with a piggybacked
      acknowledgment (acknowledgment value = RCV.NXT).  If there is
      insufficient space to remember this buffer, simply return "error:
      insufficient resources".

      If the urgent flag is set, then SND.UP <- SND.NXT-1 and set the
      urgent pointer in the outgoing segments.


    FIN-WAIT-1 STATE
    FIN-WAIT-2 STATE
    CLOSING STATE
    LAST-ACK STATE
    TIME-WAIT STATE

      Return "error:  connection closing" and do not service request.