 <p>So it turned out, that there was something wrong with the connection. It was created with that code:</p> <pre><code>void PostgresqlDatabase::pgMDBconstruct(std::string host, std::string port, std::string user, std::string password, std::string dbname ) { std::string conn_info = "host=" + host + " port=" + port + " user=" + user + " password=" + password + " dbname=" + dbname; connection_= PQconnectdb(conn_info.c_str()); if (PQstatus(connection_)!=CONNECTION_OK) { ROS_ERROR("Database connection failed with error message: %s", PQerrorMessage(connection_)); } } </code></pre> <p>With <code>host=192.168.10.100, port=5432, user=turtlebot, password= , dbname=rosdb.</code><br> But an empty username doesn't satisfy the usage of PQconnectdb, which, for some parsing-reason, caused it to login to the database "turtlebot". That database unfortunately existed on my server. And there it - of course - didn't get any notifications sent out in the "rosdb"-database and had a good connection.</p> <p>What an, for me, awkward and unlucky behaviour.</p>