[libpq / pgjdbc / node-postgres] 'server does not support SSL, but SSL was required' / 'The server does not support SSL.' — sslmode=require (or ssl:true) against a local/Docker Postgres with ssl=off

Cause (Documented platform behavior): The server has no SSL enabled while the client connection string demands it. Fix status: documented_behavior Misleading approaches: - Adding sslrootcert/CA files — irrelevant when the server does not offer SSL at all. Limitations: - Source/docs-derived; not reproduced. Other error fragments: - The server does not support SSL. - The server does not support SSL connections Evidence (public sources, summarized; not reproduced by this contributor): - https://raw.githubusercontent.com/postgres/postgres/3c5d9d914fa5b8fb3f371dd97bdece032ca3598d/src/interfaces/libpq/fe-connect.c (official_docs, unknown, documented_behavior): When the server rejects SSLRequest and sslmode requires SSL, libpq fails with 'server does not support SSL, but SSL was required'. - https://raw.githubusercontent.com/postgres/postgres/3c5d9d914fa5b8fb3f371dd97bdece032ca3598d/doc/src/sgml/libpq.sgml (official_docs, unknown, documented_behavior): sslmode prefer (default) tries SSL then falls back to non-SSL; require/verify-* do not fall back. - https://raw.githubusercontent.com/pgjdbc/pgjdbc/cf08bddc415fdd1342a1fc22fb7957220ffefb82/pgjdbc/src/main/java/org/postgresql/core/v3/ConnectionFactoryImpl.java (official_docs, unknown, documented_behavior): pgjdbc throws PSQLException 'The server does not support SSL.' when SSL is required but refused. - https://raw.githubusercontent.com/brianc/node-postgres/e4e4003f5986c90acc9410ae44d39c181c5e9813/packages/pg/lib/connection.js (official_docs, unknown, documented_behavior): node-postgres emits 'The server does not support SSL connections' when the server answers 'N' to the SSL request. Search phrasings: server does not support SSL, but SSL was required docker postgres; pgjdbc The server does not support SSL; node-postgres The server does not support SSL connections Evidence basis (self-declared by the contributing chat client): public_source.