TCP/IP Problem

[ibrahim eren]

Hello, while the server is running as a TCP Server and the settings are as follows:

Behavior = Master
ClientLifetime = 30
ConnectionMode = Shared
DeviceMapping = ByIPAddress
TcpPort = 502

we are unable to establish a connection when trying to connect a second 4G modem as a client to SCADA. We also cannot establish a connection when attempting to connect using the Modbus Tools Slave test program.

[Mikhail]

Hello,
Usually 4G modems are not available by IP from outside. Telecom operators sell white IP addresses. Another solution is using VPN.

[Mikhail]

If a communication line is working as TCP server, make sure that incoming connections are enabled in the firewall settings.

[ibrahim eren]

Can you share a screenshot of a setup where the TCP Server is running and multiple modems are connected as clients? I think there was a misunderstanding. The server allows one client, but when multiple clients try to connect, it disconnects the connections beyond the first one. We have modems using dynamic IPs and do not want to use static IPs. Please share an example setup.

[zzz]

So this is a reversely connected Modbus TCP setup.
ConnectionMode = Shared doesn’t seem logically possible. I think it only make sense for RTU over TCP when multiple device go through the same TCP Gateway ?

[zzz]

@MikHail: What is ByDriver mode, is the usually omitted modbus-tcp station number used?

[Mikhail]

The existing configurations belong to project owners, so can’t be shared. Provide screenshots of your settings to check.
Note that after connection a modem should send a “hello packet” to identify a device. If it’s not supported by the modem, you need to use different TCP port for each device.

[Mikhail]

ByDriver means that a driver parses an incoming request to decide what device the request belongs to. It is usually used in slave mode when we cannot identify device by IP or hello packet.

[Author]

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