uint32_t guess_netmask(uint32_t ip);
int get_null_fd(void);
+int tcp_open_active(const char *target, uint16_t default_port,
+ struct sockaddr_in *sinp, int *fdp);
+int tcp_open_passive(const char *target, uint16_t default_port);
+
int read_fully(int fd, void *, size_t, size_t *bytes_read);
int write_fully(int fd, const void *, size_t, size_t *bytes_written);