+/** \cond Userland defines for Linux DCCP support. */
+#ifndef IPPROTO_DCCP
+#define IPPROTO_DCCP 33 /**< IANA assigned value */
+#define SOCK_DCCP 6 /**< Linux socket type */
+#define SOL_DCCP 269 /**< Linux socket level */
+#endif
+/** \endcond */
+
+/**
+ * Generic socket creation (passive and active sockets).
+ */
+extern int makesock(unsigned l3type, unsigned l4type, int passive,
+ const char *host, unsigned short port_number);
+extern struct in_addr extract_v4_addr(const struct sockaddr_storage *ss);
+
+/**
+ * Functions to support listening sockets.
+ */
+/** How many pending connections queue of a listening server will hold. */
+#define BACKLOG 10
+extern int para_listen(unsigned l3type, unsigned l4type, unsigned short port);
+
+/** Pretty-printing of IPv4/6 socket addresses */
+extern char *local_name(int sockfd);
+extern char *remote_name(int sockfd);
+
+/** used to crypt the communication between para_server and para_client */