Description:
EMS client's FT connection is terminated by the EMS server due to a missing heartbeat from the client side.
Symptoms:
Test scenario: EMS client application is running on a Linux VMware machine and creates a FT connection to the EMS server running on another Linux machine. The client/server heartbeat and timeout parameters are configured in the EMS server. The FT connection is randomly terminated by the EMS server due to missing heartbeats from the client side. The EMS client will try to reconnect to the EMS server. If the reconnection happens before the EMS server purges the connection, the reconnection will succeed, otherwise the reconnection will fail. After the client reconnects to the EMS, the same situation could happen again, that is, the connection is terminated by the EMS server due to missing heartbeats and the EMS client tries to reconnect. The client application has be restarted to resolve this issue.

From the tcpdump captures on both the EMS client and EMS server machines, it shows the TCP segments are truncated by 4 bytes and then the retransmission happens. Once the retransmission happens, the packets are only sent from the EMS server machine to the EMS client machine. So the EMS client heartbeat could not be received by the EMS server and then the EMS server will terminate the client connection due to a missing heartbeat.
Cause:
This is due to a VMware issue. A similar issue was reported on the VMware website: https://communities.vmware.com/thread/481522

EMS client's FT connection is terminated by the EMS server due to a missing heartbeat from the client side.

The customer upgraded the VMware driver from e1000 to VMX3NET in their VMware machines.The packets are going through successfully.This proved that the issue is with the VMware e1000 driver which is causing the packet loss and retransmission, which leads to disconnection.