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server-api-inet_pton

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原型

This function converts the character string src into a network address structure in the af address family, then copies the network address structure to dst. The af argument must be either AF_INET or AF_INET6.

将ip地址转换成网络2进制地址

这函数是随IPv6出现的新函数，对于IPv4地址和IPv6地址都适用。函数名中的p和n非别代表表达（presentation）和数值（numeric）。地址的表达格式通常是ASCII字符串，数值格式则是存放到套接字地址结构中的二进制值。

函数原型
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// af
//      地址类型，必现是AF_INET或AF_INET6
// src
//      要转换的ip地址
// dst
//      用于接收转换后的网络二进制的地址
//
// return:
//      inet_pton() returns 1 on success (network address was successfully converted).  0 is  returned if  src does not contain a character string representing a valid network address in the speci‐fied address family.  If af does not contain a valid address family, -1 is returned and  errno is set to EAFNOSUPPORT.
//      若成功则为1,若输入不是有效的表达格式则为0,若出错则为-1
//
int inet_pton(int af, const char *src, void *dst);

使用参考

支持一个客户端的回射服务器
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#include<unistd.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<arpa/inet.h>

#include<stdlib.h>
#include<stdio.h>
#include<errno.h>
#include<string.h>

#define ERR_EXIT(m)\
    do\
    {\
        perror(m); \
        exit(EXIT_FAILURE); \
    }while (0)

int main(void)
{
    int listenfd;
    /*if ((listenfd = socket(PF_INET, SOCK_STREAM, 0))<0)*/
    if ((listenfd = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0)
        ERR_EXIT("socket");

    struct sockaddr_in servaddr;
    memset(&servaddr, 0, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_port = htons(5188);
    // inet_aton("127.0.0.1", &servaddr.sin_addr);
    // servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    // servaddr.sin_addr.s_addr = inet_addr("127.0.0.1");
    inet_pton(AF_INET, "127.0.0.1", &servaddr.sin_addr);

    int on = 1;
    if(setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
        ERR_EXIT("SETSOCKOPT") ;

    if (bind(listenfd, (struct sockaddr*)&servaddr, sizeof(servaddr)) < 0)
        ERR_EXIT("BIND");

    if (listen(listenfd, SOMAXCONN) < 0)
        ERR_EXIT("LISTEN");

    struct sockaddr_in peeraddr;
    socklen_t peerlen = sizeof(peeraddr);
    int conn;
    if ((conn = accept(listenfd, (struct sockaddr*)&peeraddr, &peerlen)) < 0)
        ERR_EXIT("ACCEPT");

    printf("ip=%s port=%d\n", inet_ntoa(peeraddr.sin_addr), ntohs(peeraddr.sin_port));

    char recvbuf[1024];
    while (1)
    {
        memset(recvbuf, 0, sizeof(recvbuf));
        int ret = read(conn, recvbuf, sizeof(recvbuf));
        fputs(recvbuf, stdout);
        write(conn, recvbuf, ret);
    }

    close(conn);
    close(listenfd) ;

    return 0;
}