This is the swift structures:
// swift interface
typedef struct swift {
	int socketListener, socketData;
	struct sockaddr_in socketListenerAddr;
} *Swift;

// swift_addr structure similar with in_addr 
struct swift_addr {
	unsigned short N;			// e.g. number of s_addr
	unsigned long s_addr[MAX_IPs];		// i.p. ip list
};

// swift struct similar with sock_addr
typedef struct sockSwiftaddr {
    short		sin_family;		// e.g. AF_INET
    unsigned short	sin_port;		// e.g. htons(3490)
    struct swift_addr   sin_addr;		// see struct swift_addr, below
} *SockSwiftaddr;

// list of swift_addr
struct listsockaddr {
	unsigned short N;
	struct sockaddr_in sa[MAX_IPs];
};

With this new structures we modify the normal socket api and the new api is:

// Function to create a Swift socket
Swift socketSwift();

// Function to close a Swift socket
void closeSwift(Swift);

// Function to listen to a port
int listenfromSwift (Swift s, void *buf, size_t len, int flags,
                 struct sockSwiftaddr * __restrict__ from, socklen_t *fromlen);

// Function to bind a port for swift socket
int bindSwift(Swift s, const struct sockSwiftaddr *my_addr, socklen_t addrlen);

// Function to receive a message
ssize_t recvFromSwift(Swift s, void *buf, size_t len, int flags,
                 struct sockSwiftaddr *from, socklen_t *fromlen);
                 
// Function to send a message
ssize_t sendToSwift(Swift s, const void *buf, size_t len, int flags, 
				const struct sockSwiftaddr *to, socklen_t tolen);