Linux网络编程IPv4和IPv6的inet_addr、inet_aton、inet_pton等函数小结

知识背景：

210.25.132.181属于IP地址的ASCII表示法，也就是字符串形式。英语叫做IPv4 numbers-and-dots notation。

如果把210.25.132.181转换为整数形式，是3524887733，这个就是整数形式的IP地址。英语叫做binary data。（其实binary是二进制的意思）

详细介绍，请参考：网络字节序与主机字节序的转换

问题所在：

如何在字符串形式的IP和整数形式的IP之间转换呢？

转换函数：

int inet_aton(const char *cp, struct in_addr *inp);

in_addr_t inet_addr(const char *cp);

in_addr_t inet_network(const char *cp);

int inet_pton(int af, const char *src, void *dst);

const char *inet_ntop(int af, const void *src, char *dst, socklen_t cnt);

参考：http://beej.us/guide/bgnet/output/html/multipage/inet_ntopman.html

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IPv4：

IP字符串 ——》 网络字节流

inet_addr、inet_network、inet_aton

程序代码：

#include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <string.h> #include <netinet/in.h> #include <sys/socket.h> #include <sys/types.h> int main() { char ip[] = "192.168.0.74"; long r1, r2, r3; //long struct in_addr addr; r1 = inet_addr(ip); //返回网络字节序 if(-1 == r1){ printf("inet_addr return -1/n"); }else{ printf("inet_addr ip: %ld/n", r1); } r2 = inet_network(ip); //返回主机字节序 if(-1 == r2){ printf("inet_addr return -1/n"); }else{ printf("inet_network ip: %ld/n", r2); printf("inet_network ip: %ld/n", ntohl(r2)); //ntohl: 主机字节序 ——> 网络字节序 } r3 = inet_aton(ip, &addr); //返回网络字节序 if(0 == r3){ printf("inet_aton return -1/n"); }else{ printf("inet_aton ip: %ld/n", addr.s_addr); } /***** 批量注释的一种方法 *****/ #if 0 r3 = inet_aton(ip, addr); if(0 == r3){ printf("inet_aton return -1/n"); }else{ printf("inet_aton ip: %ld/n", ntohl(addr.s_addr)); } #endif return 0; }

运行结果：

[[email protected] net]$ gcc -W -o inet_addr inet_addr.c
[[email protected] net]$ ./inet_addr
inet_addr ip: 1241557184
inet_network ip: -1062731702
inet_network ip: 1241557184
inet_aton ip: 1241557184

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IP字符串 《——》 网络字节流

inet_addr、inet_aton、inet_ntoa

程序代码：

#include <stdio.h> #include <sys/socket.h> #include <netinet/in.h> #include <arpa/inet.h> #include <string.h> int main(int argc, char *argv[]) { char ip1[] = "192.168.0.74"; char ip2[] = "211.100.21.179"; struct in_addr addr1, addr2; long l1, l2; l1 = inet_addr(ip1); //IP字符串——》网络字节 l2 = inet_addr(ip2); printf("IP1: %s/nIP2: %s/n", ip1, ip2); printf("Addr1: %ld/nAddr2: %ld/n", l1, l2); memcpy(&addr1, &l1, 4); //复制4个字节大小 memcpy(&addr2, &l2, 4); printf("%s <--> %s/n", inet_ntoa(addr1), inet_ntoa(addr2)); //注意：printf函数自右向左求值、覆盖 printf("%s/n", inet_ntoa(addr1)); //网络字节 ——》IP字符串 printf("%s/n", inet_ntoa(addr2)); return 0; }

运行结果：

[[email protected] net]$ gcc -W -o inet_ntoa inet_ntoa.c

[[email protected] net]$ ./inet_ntoa

IP1: 192.168.0.74

IP2: 211.100.21.179

Addr1: 1241557184

Addr2: 3004523731

192.168.0.74 <--> 192.168.0.74

192.168.0.74

211.100.21.179

=============================================================

IPv6：

IPv4 字符串 《——》网络字节流

inet_pton、inet_ntop

程序代码：

#include <stdio.h> #include <sys/types.h> #include <sys/socket.h> #include <arpa/inet.h> int main() { char ip[] = "192.168.0.74"; struct in_addr addr; int ret = inet_pton(AF_INET, ip, (void *)&addr); //IP字符串 ——》网络字节流 if(0 == ret){ printf("inet_pton error, return 0/n"); return -1; }else{ printf("inet_pton ip: %ld/n", addr.s_addr); printf("inet_pton ip: 0x%x/n", addr.s_addr); } const char *pstr = inet_ntop(AF_INET, (void *)&addr, ip, 128); //网络字节流 ——》IP字符串 if(NULL == pstr){ printf("inet_ntop error, return NULL/n"); return -1; }else{ printf("inet_ntop ip: %s/n", ip); } return 0; }

运行结果：

[[email protected] net]$ gcc -W -o inet_ptoa inet_ptoa.c
[[email protected] net]$ ./inet_ptoa
inet_pton ip: 1241557184
inet_pton ip: 0x4a00a8c0
inet_ntop ip: 192.168.0.74

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IPv6 字符串 《——》网络字节流

inet_pton、inet_ntop

程序代码：

#include <stdio.h> #include <stdlib.h> #include <string.h> #include <arpa/inet.h> int main(int argc, char **argv) { unsigned char buf[sizeof(struct in6_addr)]; int domain, s; char str[INET6_ADDRSTRLEN]; if(argc != 3){ fprintf(stderr, "usage: %s {i4|i6|<num>} string/n", argv[0]); exit(EXIT_FAILURE); } domain = (strcmp(argv[1], "i4") == 0) ? AF_INET:(strcmp(argv[1], "i6") == 0) ? AF_INET6 : atoi(argv[1]); //IP字符串 ——》网络字节流 s = inet_pton(domain, argv[2], buf); if(s<=0){ if(0 == s) fprintf(stderr, "Not in presentation format/n"); else perror("inet_pton"); exit(EXIT_FAILURE); } //网络字节流 ——》IP字符串 if(inet_ntop(domain, buf, str, INET6_ADDRSTRLEN) == NULL){ perror("inet ntop/n"); exit(EXIT_FAILURE); } printf("%s/n", str); exit(EXIT_SUCCESS); } 运行结果：

[[email protected] net]$ gcc -W -o inet_ptoa6 inet_ptoa6.c
[[email protected] net]$ ./inet_ptoa6 i6 0:0:0:0:0:FFFF:204.152.189.116
::ffff:204.152.189.116
[[email protected] net]$ ./inet_ptoa6 i4 204.152.189.116
204.152.189.116

参考：http://www.kernel.org/doc/man-pages/online/pages/man3/inet_pton.3.html