S7-300 MOSBUSPN can connect only to one client

I have a project with PLC S7-315-2 that is a server in MODBUS, using MODBUSPN.

The problem is that only one client can connect to it and I can't find where to change it so more that can can be connected at the same time.

I tried in the CPU properties (see attached) but it didn't work

Hello StamGuy,

from basic principle, this isn't possible. If Server reserves one Port (502 in this case as std MB TCP), only one Client can connect at time to this Port. If you want another Client connection possible, you needd define new MB TCP connection with diffrent MB TCP Port (503,...). Then new Client can connect to this Server's different port and Server can share data to more Clients. It can be possible share one Port (as is your situation now) but you then need do some connection state machine and do Client's IP handling with cycle each of Clients to allow connect them what can be problem in some situations. I recommend read basic documentation from web about TCP/IP protocols, connections, this isn't strictly Siemens problematic but general. Your screenshot also points to general resources about number of connections but MB TCP isn't native here and also you need take care only about OUC number of connections to have enough, here it is about expected number of Clients that want connect to your Server f.ex.

Update: if I could recommend also, your Topic name is also not correct probably, I recommend fix it with correct description.