TCP Connection idle timeout#108
Conversation
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Hi Anatoly, thanks, I'll take a look and come back to you. For testing, all the 3rd-party tools required are included in the package and are installed when you run the tests. |
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I've tweaked you changes a little and built them into a 2.7.0-SNAPSHOT from the development branch so please download and see if it looks good and I will make a master release |
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Hi Steve, thank you, Your tweaks are all fine. Wrt tests: I'm working on Linux (CentOS 6) and I had problem running tests based on "modpoll" utility. 13:01:51 anatoly@anatoly modpoll-1597053427810> ./modpoll -m tcp -p 2502 -a 15 -r 1 -t 0 -c 1 localhost 0 Protocol configuration: MODBUS/TCP Can't reach server/slave! Check TCP/IP and firewall settings. Protocol configuration: MODBUS/TCP Written 1 reference. So, it works with 127.0.0.1, but doesn't work with "localhost". Slave is listening "all interfaces", as expected: 13:01:45 anatoly@anatoly modpoll-1597053427810> netstat -apn | grep 2502 and "locahost" resolves right: I will look on it further, when I have more time. Should be some local configuration issue, I think. |
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Swapped to using 127.0.0.1 in the tests and released 2.7.0 |
…imeout - Activates j2mod timeout. See steveohara/j2mod#108 - Add `LogVerbosity` to Modbus API Controllers. Count and display "Access" and "Write" to Registers. - Refactor `CommonConfig` for all Modbus API Controllers Co-authored-by: Michael Grill <[email protected]> Co-authored-by: Kai Jeschek <[email protected]> Reviewed-by: Kai Jeschek <[email protected]>
2 participants
Hi Steve,
First, thank you very much for working on j2mod. I've been using original jamod for quite a while in my projects and I was always worried about its error handling / etc being a bit "childish". j2mod code looks much better.
Still, there is an issue.
My Modbus/TCP slaves sometimes get unresponsive - it will accept incoming connections but will never respond anything. I tracked it to be the cases where connection suddenly drops. For examples, master devices being abruptly powered off of a LAN cable being disconnected.
TCP connection will not detect any timeouts if it is not actively sending any data. So, if LAN cable is disconnected between requests, ModbusTCPTransport will simply hang in Socket.read(), waiting for data which will never arrive and occupying a thread in a thread pool. Eventually thread pool becomes depleted and slave doesn't process any more requests.
There is a couple of bugs in JDK (https://bugs.java.com/bugdatabase/view_bug.do?bug_id=8075484 and relates), which are "fixed" but are still reproducable on some machines (I've been using 8u201 on CentOS 6 and it is still there).
Please review this pull request.
I've added a watchdog timer for TCP connection, which closes the connection if there is no activity within a given timeframe. This works as a safety net - if master dies, a connection will eventually be closed and release the thread in thread pool.
Please feel free to request any changes, if proposed changes doesn't suite your design (it seems to me that TCPConnectionHandler is a right place for the watchdog, but I'm not sure), I will do them.
Sincerely, Anatoly
P.S. I couldn't find a documentation on building / running unit tests, please would you point me there, if it exists.
Some tests (TestModbusTCPExternalRead, for example) seems to rely on some external tool (?) and I was unable to run them.