RECEIVE Call

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

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

      Otherwise return "error:  connection does not exist".

    LISTEN STATE
    SYN-SENT STATE
    SYN-RECEIVED STATE

      Queue for processing after entering ESTABLISHED state.  If there
      is no room to queue this request, respond with "error:
      insufficient resources".

    ESTABLISHED STATE
    FIN-WAIT-1 STATE
    FIN-WAIT-2 STATE

      If insufficient incoming segments are queued to satisfy the
      request, queue the request.  If there is no queue space to
      remember the RECEIVE, respond with "error:  insufficient
      resources".

      Reassemble queued incoming segments into receive buffer and return
      to user.  Mark "push seen" (PUSH) if this is the case.

      If RCV.UP is in advance of the data currently being passed to the
      user notify the user of the presence of urgent data.

      When the TCP takes responsibility for delivering data to the user
      that fact must be communicated to the sender via an
      acknowledgment.  The formation of such an acknowledgment is
      described below in the discussion of processing an incoming
      segment.


    CLOSE-WAIT STATE

      Since the remote side has already sent FIN, RECEIVEs must be
      satisfied by text already on hand, but not yet delivered to the
      user.  If no text is awaiting delivery, the RECEIVE will get a
      "error:  connection closing" response.  Otherwise, any remaining
      text can be used to satisfy the RECEIVE.

    CLOSING STATE
    LAST-ACK STATE
    TIME-WAIT STATE

      Return "error:  connection closing".