SG Security Communications MLR2-E Manual do Utilizador descarregar pdf (Página 54)

Form Number.: 7-3005 File Name: SG Automation Output Revision/Date: 01/May 3, 2005

Department: Engineering

Division: Embedded Software Form Template Owner: Jeff Cougler

6.3 TCP/IP Connection Description

The Automation “Client” attaches a socket to the CPM “server” as per the following diagram after Stevens “Unix Network

Programming” Prentice Hall 1990 section 6.2.

socket ()

bind ()

listen ()

accept ()

read ()

write ()

socket ()

connect ()

write ()

read ()

Client (Automation)

Server (CPM)

Connection Oriented Protocol

connection establishment

data (request)

data (reply)

6.4 Automation Responses

When the CPM sends an alarm to the automation, it checks for 3 types of responses:

Signal Value Condition

ACK 06H automation got the event successfully

NAK 15H automation got the message but data was invalid

No response Automation absent, not connected

If a value is sent by the automation that is not known by the receiver (for example a corrupted ACK), it will be ignored by the

receiver and the previous alarm will be resent.

An ACK tells the CPM the automation got the event successfully. A NAK tells the CPM the automation got the message but

didn’t understand it. The CPM will attempt to send the message 20 times. If after 20 attempts it continually got NAK from the

automation, the CPM will send a communication error message to the printer, and then begin attempting to send the next event

in the buffer to the automation. Any other response from the automation, including no response will cause the CPM to attempt

to send the message again, up to 4 attempts. If after 4 attempts the CPM got no response or an unknown response, it will

generate an output failure.

6.4.1 Automation Command Packets

Figure 1 Socket system calls for connection-oriented protocol

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SG Security Communications MLR2-E Manual do Utilizador Página 54