c语言的tcp和udp客户端和服务器

int main(int argc, const char *argv[])
{
    int listenfd, acceptfd;
    struct sockaddr_in sin, cin;
    socklen_t clen;
    char buf[1024];

    signal(SIGCHLD, SIG_IGN);

    listenfd = socket(PF_INET, SOCK_STREAM, 0);

    sin.sin_family = PF_INET;
    sin.sin_port = htons(atoi(argv[2]));
    sin.sin_addr.s_addr = inet_addr(argv[1]);
    bind(listenfd, (struct sockaddr *)&sin, sizeof(sin));

    listen(listenfd, 5);

    while(1)
    {
        clen = sizeof(cin);
        printf("listen ......
");
        acceptfd = accept(listenfd, (struct sockaddr *)&cin, &clen);
        printf("client %s %d connect
", inet_ntoa(cin.sin_addr), ntohs(cin.sin_port));

        if(fork() == 0)
        {
            close(listenfd);

            while(1)
            {
                bzero(buf, sizeof(buf));
                if(recv(acceptfd, buf, sizeof(buf), 0) == 0)
                {
                    printf("client %s %d exit
", inet_ntoa(cin.sin_addr), ntohs(cin.sin_port));
                    exit(0);
                }
                printf("recv(%s %d): %s
", inet_ntoa(cin.sin_addr), ntohs(cin.sin_port), buf);
            }
        }

        close(acceptfd);
    }

    return 0;
}

int main(int argc, const char *argv[])
{
    int cfd = socket(PF_INET, SOCK_STREAM, 0);
    struct sockaddr_in cin;
    char buf[1024];

    cin.sin_family = PF_INET;
    cin.sin_port = htons(atoi(argv[2]));
    cin.sin_addr.s_addr = inet_addr(argv[1]);
    connect(cfd, (struct sockaddr *)&cin, sizeof(cin));

    printf("connect ip(%s) port(%s) server ok
", argv[1], argv[2]);

    if(fork() == 0)
    {
        while(1)
        {
            bzero(buf, sizeof(buf));
            recv(cfd, buf, sizeof(buf), 0);
            printf("recv: %s
", buf);
        }
    }

    while(1)
    {
        fgets(buf, sizeof(buf), stdin);
        buf[strlen(buf)-1] = '