Session Layer - Test Request

A Test Request (tag 35-MsgType=1) message is sent to ensure connectivity. This message can be sent by both the client system and CME Globex. 

If connectivity is in question, for example, a Heartbeat (tag 35-MsgType=0) message has not been received at the defined interval, the following should occur:

1. A Test Request (tag 35-MsgType=1) message is sent.

2. A Heartbeat (tag 35-MsgType=0) message is sent in response with tag 112-TestReqID from the original Test Request message.

3. If no Heartbeat (tag 35-MsgType=0) message is received in response to the Test Request (tag 35-MsgType=1) message within the defined hearbeat interval, the connection is assumed to be stale and the socket is closed.

4. If the connection being closed is the primary connection and the client employs fault tolerance, iLink 2 initiates a failover process to make one of the backup connections, if existent, the new primary.

5. If the client does not employ fault tolerance, CME Globex updates the status of that client to 'logged out'.

6. A Test Request (tag 35-MsgType=1) message is sent only to ensure connectivity, and as a handshake
   upon logon.

The following diagram illustrates the successful Test Request (tag 35-MsgType=1) message flow.