4D requires an uninterrupted network communication. If a socket opened by 4D is closed from a device in the network, the connection breaks and a restart is required. This is not a bug, 4D is designed to need a stable network

The Idle Connection Timeout database parameter places an idle socket connection into a postponed state, this is a graceful closure of the communication socket that is mutually accepted by both the 4D Client and the 4D Server. This feature is exposed via Set Database Parameter selector 54 and it is intended to help prevent disconnections when a router or other device on the network is configured to close idle socket connections.

Although the Idle Connection Timeout feature has existed since v11, it is important to understand that this feature is not available when Encrypted Client-Server Communication is enabled.

Therefore, if using encrypted client-server communication, it is critical that the network be setup so that all involved devices do not close connections on their own, including connections that may be considered as “IDLE”. To do so, either disable IDLE close connection totally or set exceptions for the used IP addresses and port ranges. To learn how to do so, contact the vendor of the used devices, such as routers and managed switches.