对两个数求和的str_echo函数

void str_echo(int sockfd) {
    long arg1, arg2;
    ssize_t n;
    char line[MAXLINE];

    for ( ; ; ) {
        if ( (n = read(sockfd, line, MAXLINE)) == 0) {
            return;
        }
        if (sscanf(line, "%ld%ld", &arg1, &arg2) == 2) {
            snprintf(line, sizeof(line), "%ld\n", arg1+arg2);
        } else {
            snprintf(line, sizeof(line), "input error\n");
        }
        n = strlen(line);
        writen(sockfd, line, n);
    }
}