Bug #122686 for Device-Modbus-TCP: write_multiple_registers() generates a malformed request when sending more than 123 registers

> Hi there: > > > With Modbus TCP, you can only write up to 123 registers at once with > write_multiple_registers(). This limit is imposed by the Modbus TCP > protocol. > > However, if you try to send more registers, module Device::Modbus::TCP > just sends a malformed request. I think the upper bit gets set, which > means that an exception code is sent as a Modbus request. The server > rejects it accordingly. > > I think the client should check and throw an exception (with "die") to > the caller instead of sending a malformed request. > > Other than that, many thanks for the module! > > > Best regards, > rdiez

> Hello! > > Actually, the client does find and reject the request. The problem is > that it is treated unexpectedly: Instead of dying, it returns an > exception *response* as if it was the server. But the client does not > die: > > my $client = Device::Modbus::TCP::Client->new( port => 6545 ); > > my $req = $client->write_multiple_registers( > function => 'Write Multiple Registers', > address => 1, > values => [(0x000A, 0x0102) x 62], # results in 124 registers > ); > > isa_ok $req, 'Device::Modbus::Exception'; > is $req->{code}, 0x90, > 'Function code is correct for a write registers request'; > is $req->{exception_code}, 3, > 'Exception code is correct for a request above 123 registers'; > > > So... I think the proper way to take this would be to just die with a > nice, explicative note. > > Thank you for your note and the time you took to report this problem. > I shall let you know by this means when the new version with the > correct behavior is out. > > Julio > > On Wed Aug 02 11:07:33 2017, rdiezmail-perl@yahoo.de wrote: