TCP Server Connection Issue

[ibrahim eren]

Hello, I am setting up SCADA as a TCP server and my 4G modem as a TCP client. There is a Modbus RTU slave behind my 4G modem, and everything works correctly. However, sometimes even if the SCADA side drops the socket connection, it does not inform the 4G modem that the connection has been terminated. As a result, the modem does not terminate the socket connection, causing a communication breakdown. The modem appears to have a TCP connection, but data cannot be exchanged. How can we solve this issue?

[Mikhail]

Hello,

In TCP communication, a connection brakes silently sometimes. If a client cannot poll a server, it must reconnect if there is no reply or connection is idle for a period.

• This reply was modified 1 year ago by Mikhail.

[zzz]

However, sometimes even if the SCADA side drops the socket connection, it does not inform the 4G modem that the connection has been terminated.

If the 4G gateway client lost connection, the server has no way to notify this client. The client must detect this itself by timeout or communication attempts. Maybe dig into the settings of this 4G modem or 4G data gateway.

[Mikhail]

As I remember Moxa NPort has such settings, for example.

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