ION8650 as modbus master/clients connection limitation

[Liangchen1982]

Hello SE experts:

in Modbus master options modules, the TCP connection maximum is 20. Does that mean ION8650A as a modbus client can talk to 20 modbus master devices?  Then how about the maximum 8 ethernet socket connections limitations?

I was told the meter can only accept 8 client requests or sockets for client request polls like Modbus Master or DNP Master requests. As a server the meter can only respond to 8 clients at a time. But, as a client it can make additional requests to server devices on top of clients the meter is responding to. (up to 14? or 20??)

it is still a bit confused. please help explain.

[Charles_Murison · Accepted solution]

Hello @Liangchen1982 ,

Rather than saying server/client I will use incorrect terms but easier to understand incoming and outgoing. Incoming means something outside the meter is initiating the connection and polling device for information. Outgoing means meter is starting the connection request and meter wants the data.

Different protocols have different limits. DNP for example is limited to only 3 in coming connections. IEC61850 is limited to 5. ION can have 8, but only if only ION connections. The meter can support a maximum of 8 simultaneous or concurrent connections. If meter has 2 DNP clients connected, 1 IEC61850 client connected, 1 Ethergate connection, there is room for only 4 ION connections.

Outgoing connections does not have to follow the 8 connection limitation. Modbus master options modules, the TCP connection I see has a maximum of 10. This means, the meter can make 10 out going connections, the meter can make modbus requests to the external device. 

Hope this helps.

Regards,

Charles

[Liangchen1982]

Thanks Charles, very appreciated.