一、C#簡單helloworld程式

1.用C#編寫一個命令列/控制檯hello world程式，實現如下功能：在螢幕上連續輸出50行“hello cqjtu！重交物聯2018級”；

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace helloworld控制檯
{
    class Program
    {
        static void Main(string[] args)
        {
            for (int i = 0; i < 50; i++)
            {
                Console.WriteLine("hello cqjtu!重交物聯2018級");
            }
            Console.ReadKey();
        }
    }
}
 

2.建立一個server伺服器和client進行通訊程式設計

伺服器程式碼

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Net.Sockets;
using System.Net;

namespace server
{
    class Program
    {
        static void Main(string[] args)
        {
            UdpClient udpRec = new UdpClient(8888);
            Console.WriteLine("伺服器已開啟！");
            try
            {
                while (true)
                {
                    IPEndPoint remoteIpEndPoint = new IPEndPoint(IPAddress.Any, 0);
                    byte[] recBytes = udpRec.Receive(ref remoteIpEndPoint);
                    string returnData = Encoding.Default.GetString(recBytes);
                    Console.WriteLine("接收到的資料是:" + returnData);
                }
            }
            catch (Exception e)
            {
                Console.WriteLine(e);
            }
            finally
            {
                udpRec.Close();
            }
        }
    }
}


 

客戶端程式碼：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Net.Sockets;
using System.Net;


namespace client
{
    class Program
    {
        static void Main(string[] args)
        {
            int j = 0;
            while (j < 50)
            {
                Console.WriteLine("hello cqjtu!重交物聯2018級");
                j++;
            }
            UdpClient client = new UdpClient("127.0.0.1", 8888);
            Console.WriteLine("正在準備傳送資料！");
            try
            {
                while (j>0)
                {
                    string str = "hello cqjtu!重交物聯2018級";
                    byte[] sendBytes = Encoding.Default.GetBytes(str);
                    client.Send(sendBytes, sendBytes.Length);
                    j--;  
                }
            }
           
            catch (Exception e)
            {
                
                Console.WriteLine(e);
            }
            finally
            {
                client.Close();
            }
            Console.WriteLine("資料傳送成功！");
            Console.Read();
        }
    }
}


 

二、寫一個Form視窗程式

用VS2015/2017 的C#編寫一個簡單的Form視窗程式，有一個文字框 textEdit和一個傳送按鈕button，執行程式後，可以在文字框裡輸入文字，如“hello cqjtu物聯18!”，點選button，將這些文字傳送給室友電腦或樹莓派，採用UDP套接字；

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Net;
using System.Net.Sockets;
using System.Threading;


namespace Server
{
    public partial class Form1 : Form
    {
        private UdpClient receiveUdpClient;//接收用
        private UdpClient sendUdpClient;//傳送用
        private const int port = 8888;//和本機繫結的埠號
        IPAddress ip;//本機ip
        IPAddress remoteip;//=IPAddress.Parse("");遠端主機ip
        public Form1()
        {
            InitializeComponent();
            CheckForIllegalCrossThreadCalls = false;
            //獲取本機可用IP地址
            IPAddress[] ips = Dns.GetHostAddresses(Dns.GetHostName());
            foreach (IPAddress ipa in ips)
            {
                if (ipa.AddressFamily == AddressFamily.InterNetwork)
                {
                    ip = ipa;
                    break;
                }
            }
            //為了在同一臺機器除錯，此IP也作為預設遠端IP
             remoteip = ip;

        }

        private void Form1_Load(object sender, EventArgs e)
        {
            //建立一個執行緒接收遠端主機發來的資訊
            Thread myThread = new Thread(ReceiveData);
            myThread.IsBackground = true;
            myThread.Start();
        }

        //接收資料
        private void ReceiveData()
        {
            IPEndPoint local = new IPEndPoint(ip, port);
            receiveUdpClient = new UdpClient(local);
            IPEndPoint remote = new IPEndPoint(IPAddress.Any, 0);
            while (true)
            {
                try
                {
                    //關閉udpClient 時此句會產生異常
                    byte[] receiveBytes = receiveUdpClient.Receive(ref remote);
                    string receiveMessage = Encoding.Unicode.GetString(
                        receiveBytes, 0, receiveBytes.Length);
                    listBox1.Items.Add("收到的訊息:" + receiveMessage);
                }
                catch
                {
                    break;
                }
            }
        }
        //點擊發送按鈕傳送資料
        private void button1_Click(object sender, EventArgs e)
        {
            //remoteip = IPAddress.Parse(txt_IPAddress.Text);
            Thread myThread = new Thread(SendMessage);
            myThread.IsBackground = true;
            myThread.Start(textBox2.Text);
        }
        //傳送訊息
        private void SendMessage(object obj)
        {
            string message = (string)obj;
            sendUdpClient = new UdpClient(0);
            byte[] bytes = Encoding.Unicode.GetBytes(message);
            IPEndPoint iep = new IPEndPoint(remoteip, port);
            try
            {
                sendUdpClient.Send(bytes, bytes.Length, iep);
                listBox1.Items.Add("傳送的訊息:" + message);
                textBox2.Clear();
            }
            catch (Exception ex)
            {
                listBox1.Items.Add("傳送出錯:" + ex.Message);
            }
        }
        delegate void AddItemDelegate(ListBox listbox, string text);
        private void AddItem(ListBox listbox, string text)
        {
            if (listbox.InvokeRequired)
            {
                AddItemDelegate d = AddItem;
                //Control.Invoke 方法 (Delegate, Object[]):
                //在擁有控制元件的基礎視窗控制代碼的執行緒上，用指定的引數列表執行指定委託。
                listbox.Invoke(d, new object[] { listbox, text });
            }
            else
            {
                //Add：動態的新增列表框中的項
                listbox.Items.Add(text);

                //SelectedIndex屬性獲取單項選擇ListBox中當前選定項的位置
                //Count：列表框中條目的總數
                listbox.SelectedIndex = listbox.Items.Count - 1;

                //呼叫此方法等效於將 SelectedIndex 屬性設定為-1。 
                //可以使用此方法快速取消選擇列表中的所有項。
                listbox.ClearSelected();
            }
        }
        delegate void ClearTextBoxDelegate();
        private void ClearTextBox()
        {
            if (textBox2.InvokeRequired)
            {
                ClearTextBoxDelegate d = ClearTextBox;
                textBox2.Invoke(d);
            }
            else
            {
                textBox2.Clear();
                textBox2.Focus();
            }
        }

        private void label2_Click(object sender, EventArgs e)
        {

        }

        private void label2_Click_1(object sender, EventArgs e)
        {

        }
    }
}

三、wirshark

安裝wireshark 抓包軟體，抓取上述程式傳送的網路包，對資料幀結構進行分析
前四行分別為源埠，目的埠，長度，校驗和。
每一個各佔2byte，一共8byte。
傳送的訊息為：“你好，重慶交通大學”，一共9個字元，18byte，18+8=26，即長度。