取客户IP地址

 #include "unp.h"

int main(int argc, char **argv)
{
        int listenfd, connfd;
        struct sockaddr_in servaddr;

        if ((listenfd = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP)) == -1)
                err_sys("socket");
        bzero(&servaddr, sizeof(servaddr));
        servaddr.sin_family = AF_INET;
        servaddr.sin_port = htons(13);
        servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
        if (bind(listenfd, (SA *)&servaddr, sizeof(servaddr)) == -1)
                err_sys("bind");
        else if (listen(listenfd, LISTENQ) == -1)
                err_sys("listen");

        struct sockaddr_in cliaddr;     /* client address */
        socklen_t clilen = sizeof(cliaddr);
        char cliip[INET_ADDRSTRLEN];

        for (;;) {
                if ((connfd = accept(listenfd, (SA *)&cliaddr, &clilen )) == -1)
                        err_sys("accept");

                /* output client IP information */
                if (inet_ntop(AF_INET, &cliaddr.sin_addr, cliip, sizeof(cliip)) == NULL)
                        err_sys("inet_ntop");
                printf("Client IP information: %s port:%d/n", cliip, ntohs(cliaddr.sin_port));

                ......................................

                if (close(connfd) == -1)
                        err_sys("close");
        }

        return 0;
}