Fixed slave responding to wrong request

[NogginBops]

This makes the slave implementation not answer modbus messages not intended for the slave. Fixes #62

[steveohara]

Thanks for the fix - sorry to be a pain, but I'm getting stricter with taking code commits without unit tests. Can you check to see if there are any unit tests that cover this scenario and if not, add one?

[NogginBops]

I'll see if I can do something about the tests. :smiley:

[NogginBops]

There looks like there is a test in TestModbusSerialRTUMasterRead.java - testBadUnitIdRequest()

@Test
public void testBadUnitIdRequest() {
    try {
        master.readCoils(UNIT_ID + 10, 0, 1).getBit(0);
        fail("Failed check for invalid Unit ID");
    }
    catch (Exception e) {
        logger.info("Got expected error response (testBadUnitIdRequest) - {}", e.getMessage());
    }
}

But the question here is how the test passed before. I have no way to actually run the serial tests on actual hardware, do you have the ability to do this?

[steveohara]

I use com0com on a Windows machine to test the serial implementation

[steveohara]

Ok, I understand the problem now. However, your fix is not correct because an error response should be sent back for TCP/UDP slaves. The response should not be sent back for Serial slaves only.

I'm working on a fix now.