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server-api-inet_aton

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原型

inet_aton() converts the Internet host address cp from the IPv4 numbers-and-dots notation into binary form (in network byte order) and stores it in the structure that inp points to.

将网络地址转成网络二进制的数字然后存于参数inp所指的in_addr结构中。

函数原型
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// cp
//      a.b.c.d     Each  of  the  four  numeric  parts  specifies  a byte of the address; the bytes are assigned in left-to-right order to produce the binary address.
//      a.b.c       Parts a and b specify the first two bytes of the binary address.  Part c  is  inter‐preted as a 16-bit value that defines the rightmost two bytes of the binary address.This notation is suitable for specifying (outmoded) Class B network addresses.
//      a.b         Part a specifies the first byte of the binary address.  Part b is interpreted  as  a 24-bit  value  that  defines  the rightmost three bytes of the binary address.  This notation is suitable for specifying (outmoded) Class C network addresses.
//      a           The value a is interpreted as a 32-bit value that is stored directly into the binary address without any byte rearrangement.
//      要转换的ip地址
// inp
//      用于接收转换后的网络二进制的地址
//
// return:
//      returns nonzero if the address is valid, zero if not.
//      成功则返回非0值，失败则返回0。
//
//
int inet_aton(const char *cp, struct in_addr *inp);

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");

    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;
}