PQsocket 函数的简单验证

    /* Make a connection to the database */
    conn = PQconnectdb(conninfo);

    /* Check to see that the backend connection was successfully made */
    if (PQstatus(conn) != CONNECTION_OK)
    {
        fprintf(stderr, "Connection to database failed: %s",
                PQerrorMessage(conn));
        exit_nicely(conn);
    }

    /*
    * Sleep until something happens on the connection.  We use select(2)
    * to wait for input, but you could also use poll() or similar
    * facilities.
    */
    sock = PQsocket(conn);
    fprintf(stderr, "PQsocket result is: %d\n",sock);

    /* close the connection to the database and cleanup */
    PQfinish(conn);