Time Acquisition Program client UDP protocol irrelevant

This article is senlie original, reproduced Please retain this address: http://blog.csdn.net/zhengsenlie

/**
* UDP: the Protocol is irrelevant. Call getaddrinfo and udp_client.
**/
# Include "unp. H"


Int
Udp_client (const char * Host, const char * serv, sa ** saptr, socklen_t * lenp)
{
Int sockfd, N;
Struct addrinfohints, * res, * ressave;


// 1. Call getaddrinfo
// The Protocol address family is af_unspec, And the socket type is sock_dgram.
Bzero (& hints, sizeof (struct addrinfo ));
Hints. ai_family = af_unspec;
Hints. ai_socktype = sock_dgram;


If (n = getaddrinfo (host, serv, & hints, & res ))! = 0)
Err_quit ("udp_client error for % s, % s: % s ",
Host, serv, gai_strerror (n ));
Ressave = res;


// 2. Try the structure of each addrinfo until it is successful or reaches the end of the linked list.
Do {
// Create a socket
Sockfd = socket (res-> ai_family, res-> ai_socktype, res-> ai_protocol );
If (sockfd> = 0)
Break;/* success */
} While (RES = res-> ai_next )! = NULL );


// 3. If getaddrinfo fails or the socket creation fails, this function will terminate
If (RES = NULL)/* errno set from final socket ()*/
Err_sys ("udp_client error for % s, % s", host, SERV );


// 4. Save the server socket address Structure
* Saptr = malloc (res-> ai_addrlen );
Memcpy (* saptr, res-> ai_addr, res-> ai_addrlen );
* Lenp = res-> ai_addrlen;


// 5. Call freeaddrinfo to clear the dynamic storage space returned by getaddrinfo
Freeaddrinfo (ressave );


// 6. Return socket
Return (sockfd );
}
/* End udp_client */


Int
Udp_client (const char * Host, const char * serv, sa ** saptr, socklen_t * lenptr)
{
Return (udp_client (host, serv, saptr, lenptr ));
}


/**
* UDP: the Protocol is irrelevant. Call getaddrinfo and udp_client.
**/
# Include "unp. H"


Int
Main (INT argc, char ** argv)
{
Int sockfd, N;
Char recvline [maxline + 1];
Socklen_t Salen;
Struct sockaddr * Sa;


If (argc! = 3)
Err_quit ("Usage: daytimeudpcli1 <Hostname/IPaddress> <service/port #> ");


// 1. Use udp_client to obtain the UDP socket and server socket address Structure
Sockfd = udp_client (argv [1], argv [2], (void **) & SA, & salen );


// 2. display the server address
Printf ("sending to % s \ n", sock_ntop_host (SA, salen ));


// 3. Send a 1-byte Datagram
Sendto (sockfd, "", 1, 0, SA, salen);/* send 1-byte datasync */


// 4. Read and display the response Datagram
N = recvfrom (sockfd, recvline, maxline, 0, null, null );
Recvline [N] = '\ 0';/* null terminate */
Fputs (recvline, stdout );


Exit (0 );
}

Time Acquisition Program client UDP protocol irrelevant