W&T 57630 Manual page 83

W&T
Communication between Web-IO and the application
In contrast to TCP, there is no communication between the Web-
IO and the other communications partner when communicating via
UDP protocol. Data are exchanged using datagrams.
Normal communication takes place in polling mode. This means
the application uses command strings to request the desired
values and set the outputs.
The Web-IO always responds to a poll by returning the IP address
and port of the requesting network station.
Example 1: Query the status of Input 3, where there is a signal of
+12 V present. No administrator password was asigned for the
Web-IO
The application sends the following string to the Web-IO:
GET /input3?PW=&
The Web-IO responds as follows:
input3;ON
Example 2: Set outputs 3,4,7,9. In binary this is 0000 0010 1001
1000 , which corresponds to 0298 hex.
The administrator password for the Web-IO is: „blue"
The application sends the following string to the Web-IO:
GET /outputaccess?PW=blue&State=0298&
The Web-IO responds as follows:
output;0298
1
The Web-IO works with null-terminated strings!
This means that everything the Web-IO sends to the
application ends with a chr(0) character
Subject to errors and modifications:
Controlling the Web-IO with TCP/UDP Sockets
83