# 網路程式作業 HW2
題目連結: https://hackmd.io/@wang1234/Sy6r1wneq
## 1.使用wireshark抓DNS request/reply封包
* request封包標頭:

* reply封包標頭:

* 執行的指令: dns，附上圖片

* 程式碼:

    #include <bits/stdc++.h>
    #include <stdio.h>
    #include <winsock.h>

    int main(void)
    {
    WSADATA wsadata;
    WSAStartup (0x101, (LPWSADATA) &wsadata);

    LPHOSTENT hp;
    struct in_addr sAddr;
    sAddr.s_addr = inet_addr("140.130.41.11");

    hp = gethostbyaddr((LPSTR) &sAddr, sizeof(sAddr), AF_INET);

    printf("140.130.41.11's domain name:\n %s\n", hp->h_name);

    return 0;
    }

* 執行畫面:

## 2. 印出subnet的所有ip其domain name
* 程式碼:

    #include <bits/stdc++.h>
    #include <stdio.h>
    #include <winsock.h>
    #include <charconv>
    using namespace std;
    char req_ip[40];
    int main()
    {
        WSADATA wsadata;
        WSAStartup (0x101, (LPWSADATA) &wsadata);

        string s;
        for(int i=1; i<=255; i++)
        {
            stringstream ss;
            s = "140.130.175." + to_string(i);
            ss << s;
            ss >> req_ip;


            LPHOSTENT hp;
            struct in_addr sAddr;
            sAddr.s_addr = inet_addr(req_ip);

            hp = gethostbyaddr((LPSTR) &sAddr, sizeof(sAddr), AF_INET);

            cout << "What is " << req_ip << "'s domain name?" << endl;
            cout << "Host name: " << hp->h_name << endl << endl;
        }

        return 0;
    }

* 執行畫面:
.
.
.

## 3. 本週心得
很新奇的東西，有影片的課前預習，上起課來覺得比較輕鬆也比較聽得懂。這次有個小發現，就是在家操作，連自己數據的時候程式碼跑不出來，需要連上學校wifi才可以執行出正確答案。

#### Hint💡: 這裡可以切換網路

###### tags = `網路程式`