Request Of A Remote Client Failed - Siemens SIMATIC S7-1500 Function Manual

OPC UA communication
9.3 Using the S7-1500 as an OPC UA server
Security events detected in diagnostics
S7-1500 CPUs perform diagnostics on the following OPC UA relevant security events:
● Client-certificate is invalid (for example, syntactically or semantically incorrect, incorrect
signature, current date is not in the validity period)
● User name/password login failed (deactivated or incorrect data)
● Client wants to use a specific security policy or a specific message security mode; the
server does not support the security policy or the requested security mode.
● Client does not establish connection according to specification (OPC UA Spec) (for
example, unexpected SecureChannelID/SessionID/client Nonce)
Example
If an attempt is made to compromise communications (for example, by session hijacking,
man-in-the-middle attacks etc.), the server detects this via analysis.
9.3.6.5

Request of a remote client failed

S7-1500 CPUs as of firmware version V2.8 are able to create an entry in the diagnostic
buffer for the following events:
● Bad client requests (incorrect use)
● Service error occurred
● CPU-specific high limits of the OPC UA server were violated
Example of a faulty client request
For example, there is an incorrect request when a client addresses a node (tag) that does
not exist or if a resource is requested that does not exist.
In this case, the corresponding service that caused the fault is entered in the diagnostic
buffer and the corresponding session ID is also entered.
Service fault
If a service itself fails, the server returns a ServiceFault. In this case, the status code (Bad...)
and the according session ID are entered in the diagnostics buffer.
Example of limit violations
If a service request exceeds a CPU-specific limit, for example, number of sessions, number
of monitored items, number of subscriptions, etc., this diagnostics is entered in the
diagnostics buffer. Together with the message, it is indicated which limit has been violated.
Exception: If you summarize diagnostics and the message occurs frequently, the limit
causing the error is not entered. You receive general information that the supported
configuration limit has been violated.
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Function Manual, 11/2019, A5E03735815-AH
Communication