Basic Testing Case with USR-IO424T as Host with Private Server

Network Topological structure:

Under the host mode, network-side can inquire or set input or output port through command; in the meantime, 485 serial can also connect devices supporting Modbus rtu protocol and fulfill the data transmission between servers and terminal 485 devices. However, it can only transmit the data in the protocol format of Modbus rtu.


As the network below indicates, if the address in the inquiring data commanded by the network-side is the address of IO Controller-USR-IO424 itself, IO Controller-USR-IO424 will implement corresponding function in the light of the command; if not, data will be transparently transmitted to 485 terminal device (so the address of 485 serial must be different from that of IO Controller-IO424 (the factory setting is 17) ), and then the data returned by 485 device will be sent to server to analyze.


If the address of data sent by 485 serial is the address of IO Controller-IO424 itself, IO Controller-IO424 will implement corresponding function in accordance with the command; if not, the data will be abandoned.


Abandon data

1. RS485 of IO424 connects PC through USB to 485, and then the port can normally the router connected to the Internet through reticle to power on.

Work: if the indicator flickers, it means the firmware has been started

Net: if the indicator keeps on, it means the server is connected

WAN/LAN: if the indicator is on, it means the network is connected


if the indicator is on, it means the network is connected

2.Set the parameters of IO 424

Download the software from website:

Start the software. Click serial operation--->set the parameter of serial--->open the serial. Then, you can control corresponding DO output through DO-1/2/3/4 on the interface.




Click “shift to parameter configuration”, and then you can read the factory setting of IO 424. Then, you can change the parameter according to following steps:

485 mode: host

Registration pack: user-defined (registration pack can be closed)

Way of sending: when connected

User-defined registration pack:

Distance connection address: xx.xx.93.90

Distance connection port: 8899



If you want to change other parameters, you can change according to your demand. The parameter will come into effect after restart.

change parameters according to demand,


Install the network debugging software from the website:, or you may use other third-party network debugging software

Start the debugging software: TCP Server protocol, fill in the local IP address, port number is 8899, and then monitor

As the image below indicates, IO 424 has been connected to the server and the server has received the information of registration pack sent by IO 424:

Note: distance data transmission needs the public IP of local address, and private IP address cannot be used to connect the network

DO can be controlled to be on through sending command from server, and the case is DO_1 as below:

Note: data sent or received should be in hexadecimal

Control to close:  11 05 00 00 FF 00 8E AA. Data can be sent through server to receive the data returned from IO424, and the indicator of the device will be on.


Control to break: 11 05 00 00 00 00 CF 5A. After receiving the reply from 424, its DO-1 indicator will be off. 



Inquire the 485 serial device data through send command from server; 424 serial connect PC through USB to 485, and it can start Modbus slave to imitate terminal serial device. The slave IO is 1, and modify the value of register 0000 to 3.


Send corresponding command from server to inquire the value of register

Send 01 03 00 00 00 01 84 0A

Receive: :01 03 02 00 03 F8 45

Note: data sent or received are both in the standard Modbus rtu protocol format