New S7-1200 on the line 2 filler, 1215C DC/DC/DC, firmware 4.4 on the label, CPU in RUN. KEPServerEX 6.x with the Siemens TCP/IP Ethernet driver, model S7-1200, port 102. Channel and device both show connected in the server status bar.
Every tag comes up Bad quality, 30 of them, all in DB1. The same server and the same driver read a 315-2 PN/DP on line 1 without a problem. The event log says "Device 'Line2.Filler' read request failed, block DB1", roughly. Ping's fine, I rebooted the server box and rebuilt the device with rack 0 slot 1 and then rack 0 slot 0, no change, and DB1 isn't optimized, I checked the block properties.
What's different about the 1200 that the 300 doesn't care about? Pretty sure it's something on the CPU side and not the server, because the 315 reads all day off the same box.
Poll rate on those tags? And is the Windows firewall on the server box open for 102 outbound, or off for the test?
1000 ms scan, 30 tags, nothing heavy. Firewall off for the test, no luck either way. KEPServer log line exact: "Device 'Line2.Filler' block request failed. Block: DB1, Address: 0, Length: 8". Not sure it's a network thing at all.
Rack and slot are a red herring on a 1200, the driver only cares about them for the 300. The block request failing while the TCP connection stays up is the CPU refusing the S7 read itself, not a network thing.
Non optimized DB is right. Next layer up is what the CPU allows.
CPU properties, Protection & Security, Connection mechanisms, "Permit access with PUT/GET communication from remote partner". On the S7-1200 from firmware V4 it is unticked by default, and the S7-1500 too. The 300 has no such setting so your line 1 works.
Tick it, compile, download hardware. The tags go good within one scan. Longer version of the SCADA side is here: https://plctr.com/introduction-to-scada-systems-and-their-integration-with-plc/
PUT/GET was unticked, that was the whole of it. Ticked it under Connection mechanisms, downloaded, and all 30 tags went Good on the next 1000 ms poll, before I got back to my desk.
The 1200 refuses that kind of read until you allow it, and the driver reads exactly that way, so one checkbox and a hardware download did the lot.
The bit I still don't like is the server calling the device connected while the CPU refuses every read. Connected at TCP level I suppose, but the status bar could say more. Thanks kiran_s.
Green channel, every tag bad. Chased that on a Modbus gateway once.