Hi Woody, thank you for taking the time to reply. the modbus test software is generic not supplied with the device. i checked the comm port settings and they match. So I wonder if my serial to ethernet converters servers for some reason are not playing nice with Mango. Because they work with the test software.
Basically each modbus device is connector to a serial to ethernet converter see drawing (thetop part is description bottom part just icons of the same) and a virtual comm port is created for each device.
They also support IP so I tried MODBUS IP and get the same no response error. but if I change the ip port from the real one to a random ip port I get a timeout error. Which makes me think the connection settings are right and the request to the slave is getting through but just not getting a response from the devi0_1466476518946_ConnectionDrawingt.pdf ce.