W&T 57630 Manual page 76

W&T
Select in the navigation tree Config >> Device >> Output Mode
m
Required access rights: Administrator
All the outputs that will be used must be activated for HTTP
(factory default).
If you have changed the output modes, click on the Temporary
Storage button and then on the Save and activate all temporary
settings link. Clicking on the Save button saves all your settings.
The Web-IO now functions as a TCP server, which results in a
three-part program sequence regardless of which programming
language is used:
1. Opening of the TCP connection
The application always functions as a client and opens the TCP
connection.
The socket interface of the Web-IO is based to a great extent on
HTTP protocol. This means that the listen port is fixed as TCP-
Port 80.
1
As a protection against blocked TCP connections, the
Web-IO has a timer set for Port 80 which automatically
breaks the connection 30 seconds after it is opened if no
syntactically correct commands have been received. After a
connection has been successfully opened, the application should
therefore always send for example an output query to the Web-IO.
2. Communication between Web-IO and application
Normal communication takes place in polling mode. This means:
the client application uses the command strings to request the
desired values and set the outputs.
76
Controlling the Web-IO with TCP/UDP Sockets