R01.43
22.10.2018
Page 103
ER Error notification
If a faulty structure is transferred to the Telnet server, it sends an error message. The
Telnet server distinguishes between the following errors.
Table 12: Telnet error codes
Error code
Designation
2
Faulty command
3
Faulty value
4
Faulty Bit Address
The error message for a non-existent or incorrect bit address is defined as follows:
"ER 4\r\n"
Logout
To terminate the connection via a command,
"LO \r\n:
is sent. Please note that a space must be inserted after the LO. The message
"LI 0\r\n"
confirms the successful disconnect of the connection.
Heartbeat
The Telnet server cyclically sends a "heartbeat" during an existing connection. If this
is not received by the client, the Telnet server will terminate the connection. The "Heart-
beat" is built as follows:
"HBT 1" / "HBT 0"
The bit is changed between 1 and 0 for each "Heartbeat".
In this case, no CR and LF are sent.
Overview of Telnet commands
Table 13: Overview Telnet commands
Command
Description
Reaction
SI
Set Input: An input is set
ACK message of the
Telnet server with the cur-
rent value
GO
Get Output: Query of output
RO message of the Telnet
server with the current
value
RO
Read Output: Message of the Telnet
server with a current output value
Is sent only after a GO re-
quest
AK
Acknowledge: Acknowledgement of
the Telnet server after setting an input
Is sent only after a SI com-
mand
ER
Error message of the Telnet server in-
cluding error code
For details see ER error
message
