Session Layer - Logout

The iLink 2 Logout message both initiates and confirms the termination of a CME Globex order entry connection. When the client system sends a Logout (tag 35-MsgType=5) message, CME Globex sends a Logout Confirmation (tag 35-MsgType=5) message and terminates the session.

After sending a Logout (tag 35-MsgType=5) message, the client system should wait for a Logout Confirmation (tag 35-MsgType=5) message before closing the socket connection. Working orders are not affected by a client logout and will continue to be eligible for trades. Any message activity on working orders sent while the client is logged out will be stored and may be retreived by the client at next logon.

For clients who use fault tolerance, logging out of the primary system also logs out the backup.

CME Globex also sends a Logout (tag 35-MsgType=5) message when it detects an error contained in the message sent by a client system. For example, if the client system submits an invalid password, it is logged out.

The following figure illustrates a successful Logout scenario where the client system sends a logout message and CME Globex responds with a Logout Confirmation message.

Logout Where Sequence Number Is Lower Than Expected

If the client system sends a iLink 2 Logout message with tag 34-MsgSeqNum containing a lower sequence number than CME Globex is expecting, CME Globex automatically logs out the client system.

The following diagram illustrates this message flow.

Session-Layer-Logout-Sequence-Number-Lower

Logout Where Sequence Number Is Higher Than Expected

The following diagram illustrates the message flow for a Logout scenario where the client's outbound sequence number is higher than what CME Globex is expecting.

Session-Layer-Logout-Sequence-Number-Higher

In the diagram, the client system sends a iLink 2 Logout message which contains tag 34-MsgSeqNum=150. CME Globex detects a sequence gap.
CME Globex sends a iLink 2 Resend Request message with tag 369-LastMsgSeqNumProcessed=146 contain the value of the last message received.

The client system then must resend the messages for tag 34-MsgSeqNum=147, 148 and 149. CME Globex processes those messages.

Now the messages are in sequence, CME Gobex sends a Logout Confirmation (tag 35-MsgType=5) with tag 369-LastMsgSeqNumProcessed=150 which matches the client system Logout (tag 35-MsgType=5) message.