Transcript Chapter 11 Advanced Name and Address Conversion

Chapter 11
Advanced Name and Address
Conversion
Introduction
• gethostbyname, gethostbyaddr: protocol dependent
• getaddrinfo:
– a function providing protocol independence for
appications
– get a member of socket address structure
• getnameinfo
getaddrinfo Function
#include <stdio.h>
int getaddrinfo(const addr *hostname, const char *service,
const struct addrinfo *hints, struct addrinfo **result);
returns : 0 if OK, nonzero on error
struct info {
int ai_flags; // AI_PASSIVE, AI_CANONNAME
int ai_family; // AF_XXX
int ai_socktype; // SOCK_XXX
int ai_protocol; // 0 or IPPROTO_xxx for IPv4 and IPv6
size_t ai_addrlen; // length of ai_addr
char *ai_canonname; // ptr to cannonical name for host
struct sockaddr *ai_addr; // ptr to socket address structure
struct addrinfo *ai_next; // ptr to next structure in linked list
};
• hostname:
– a hostname or an address string(dotted-decimal for IPv4
or a hex string for IPv6)
• service
– a service name or a decimal port number string
• hints
– a null pointer or a pointer to an addrinfo structure that the
caller fills in
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ai_flags: AI_PASSSIVE, AI_CANONNAME
ai_family (an AF_xxx value)
ai_socktype (a SOCK_xxx value
ai_protocol
• Result
– a pointer to a linked list of addrinfo structures
– four addrinfo structures for hint: null, two IP address
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first IP address, SOCK_STREAM
first IP address, SOCK_DGRAM
second IP address, SOCK_STREAM
second IP address, SOCK_DGRAM
• see Figure 11.1
gai_strerror function
#include <netdb.h>
char *gai_strerror(int error);
returns: pointer to string describing error message
freeaddrinfo function
#include <netdb.h>
void freeaddrinfo(struct addrinfo *ai)
getaddrinfo Function: IPv6 and unix Domain
getaddrinfo Function:Examples
• testga
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f inet: the address family
c : the canonical name
h bsdi: the hostname
s domain: the service name
Testga -f inet -t stream -h gateway.tuc.noao.edu -s daytime
(-t socktype, -s service name)
testga -h alpha -s ftp
testga -p -s 8888 (-p AI_PASSIVE)
testga -c -p -h /local -s /tmp/test.1
host_serv function
>daytimetcpcli bsdi daytime
connected to 206.62.226.35
Fri May 30 12:33:32 1999
>daytimetcpcli aix daytime
tcp_listen function
-create a TCP socket, bind the server’s well-known port
-allow incoming connection requests to be accepted
#include “unp.h”
int tcp_listen(const char *hostname, const char *service,
socklen_t *lenptr);
Udp_client function
unconnected UDP
#include “unp.h”
int udp_client(const char *hostname, const char *service,
void **saptr, socklen_t *lenp);
udp_connect function
#include “unp.h”
int udp_connect(const char *hostname, const char *service);
udp_server function
#include “unp.h”
int udp_server(const char *hostname, const char *service,
socklen_t *lenptr);
getnameinfo function
• Takes a socket address and returns a character string
describing the host and another character nstring
describing the service
#include <netdb.h>
int getnameinfo(const struct sockaddr *sockaddr,
socklen_t addrlen, char *host, size_t hostlen, char
*serv, size_t servlen, int flags);