+/**
+ * open connection to para_server
+ *
+ * \param argc usual argument count
+ * \param argv usual argument vector
+ * \param pcd_ptr points to dynamically allocated and initialized private client data
+ * upon successful return
+ *
+ * Check the command line options given by \a argc and argv, set default values
+ * for user name and rsa key file, read further option from the config file.
+ * Finally, establish a connection to para_server.
+ *
+ * \return Positive on success, negative on errors.
+ */