C31: Unsupported frontend protocol

Category: Connection Events
SQLSTATE: 0A000 (Class 0A - Feature Not Supported: feature_not_supported)
Urgency: low

Example Postgres Log Output:

FATAL: unsupported frontend protocol 65363.12345: server supports 1.0 to 3.0


This error message indicates that the client requested a Postgres FE/BE protocol version that the server does not support.

The most likely explanation for this is programs accidentally connecting to the Postgres port and not writing the correct protocol structure. You may also see this when someone runs a port scanner against your database server.

You can find out the source IP of the broken connection from C20: Connection received when log_connections is set to on.

Recommended Action:

No action necessary.

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