+int tcp_listen(int port);
+void enable_crypt(int fd, crypt_function *recv_f, crypt_function *send_f,
+ void *private_data);
+void disable_crypt(int fd);
+
+/**
+ * A wrapper around connect(2).
+ *
+ * \param fd The file descriptor.
+ * \param addr The address to connect.
+ * \param len The size of \a addr.
+ *
+ * This should not be called directly. Always use the PARA_CONNECT macro.
+ *
+ * \return \p -E_CONNECT on errors, 1 on success.
+ *
+ * \sa connect(2), PARA_CONNECT.
+ */
+static inline int _para_connect(int fd, void *addr, socklen_t len)
+{
+ if (connect(fd, (struct sockaddr *)addr, len) == -1)
+ return -E_CONNECT;
+ return 1;
+}