typedef ssize_t (*utcp_send_t)(struct utcp *utcp, const void *data, size_t len);
typedef ssize_t (*utcp_recv_t)(struct utcp_connection *connection, const void *data, size_t len);
typedef ssize_t (*utcp_send_t)(struct utcp *utcp, const void *data, size_t len);
typedef ssize_t (*utcp_recv_t)(struct utcp_connection *connection, const void *data, size_t len);