The message sequence below is repeated in our xcom.log file every few seconds when no transfers are executing and they are filling up the log.
What is the root cause of the messages?

2019/11/25 17:10:03 TID=REMOTE PRG=xcomtcp PID=22685 IP=10.38.56.8
    XCOMU0812I Remote Secure TCP/IP Connection Requested.

2019/11/25 17:10:03 TID=REMOTE PRG=xcomtcp PID=22685 IP=10.38.56.8
    XCOMU0780E XCOMU0780E TcpIp  507: TXPI function failed with no error code.:

2019/11/25 17:10:03 TID= PRG=xcomtcp PID=22685 IP=
    XCOMU0818I Secure TCP/IP Connection Ended.

Support recreated similar symptoms in-house by executing a telnet command to the XCOM server secure port (default 8045) i.e.
Enter: telnet xcom_server_hostname 8045
Enter: Ctrl+]
Enter: q

The XCOM server xcom.log file showed messages:

2019/12/02 18:10:23 TID=REMOTE PRG=xcomtcp PID=56553 IP=10.37.7.241
    XCOMU0812I Remote Secure TCP/IP Connection Requested.

2019/12/02 18:10:25 TID=REMOTE PRG=xcomtcp PID=56553 IP=10.37.7.241
    XCOMU0780E XCOMU0780E TcpIp  507: TXPI function failed with no error code.:

2019/12/02 18:10:25 TID= PRG=xcomtcp PID=56553 IP=
    XCOMU0818I Secure TCP/IP Connection Ended

It was suggested that in customer's environment a Load Balancer e.g. an F5, might be sending similar pings to the secure port as a health check.

Release : 11.6
Component : CA XCOM Data Transport for Linux PC

It was confirmed that a Load Balancer was sending health check pings to the secure port which resulted in the messages.
NOTE: If the IP in the messages is 127.0.0.1 the root cause may still be due to a Load Balancer agent installed on the actual XCOM server.

If parameter LOG_CONNECT_MSG is set to NO in the xcom.glb file (default is YES), the number of messages can be reduced from 3 to 1 (message XCOMU0780E remains) e.g. 
CA XCOM DATA TRANSPORT FOR UNIX/LINUX 11.6.1 > XCOM Parameters > LOG_CONNECT_MSG