C# 简单HTTP客户端 源代码

一、使用 Socket 类从 HTTP 服务器接收整个网页

using System;
using System.Text;
using System.Net;
using System.Net.Sockets;

public class GetSocket
{
    private static Socket ConnectSocket(string server, int port)
    {
        Socket s = null;
        IPHostEntry hostEntry = null;

        // 获取服务器信息.
        hostEntry = Dns.GetHostEntry(server);

        // 循环地址列表以获取对应的协议类型的支持. // 很优雅
        foreach (IPAddress address in hostEntry.AddressList)
        {
            IPEndPoint ipe = new IPEndPoint(address, port);
            Socket tempSocket =
                new Socket(ipe.AddressFamily, SocketType.Stream, ProtocolType.Tcp);

            tempSocket.Connect(ipe);

            if (tempSocket.Connected)
            {
                s = tempSocket;
                break;
            }
            else
            {
                continue;
            }
        }
        return s;
    }

    // 向指定的服务器申请网页内容.
    private static string SocketSendReceive(string server, int port)
    {
        string request = "GET / HTTP/1.1\r\nHost: " + server +
            "\r\nConnection: Close\r\n\r\n";
        Byte[] bytesSent = Encoding.UTF8.GetBytes(request);
        Byte[] bytesReceived = new Byte[256];

        // 建立连接.
        Socket s = ConnectSocket(server, port);

        if (s == null)
            return ("连接失败");

        // 向服务器发送请求.
        s.Send(bytesSent, bytesSent.Length, 0);

        // 接收服务器的主页内容.
        int bytes = 0;
        string page = server + "上的网页内容: \r\n";

        // 以下块出于阻塞状态，直到接收完成.
        do
        {
            bytes = s.Receive(bytesReceived, bytesReceived.Length, 0);
            page = page + Encoding.UTF8.GetString(bytesReceived, 0, bytes);
        }
        while (bytes > 0);

        return page;
    }

    public static void Main(string[] args)
    {
        string host;
        int port = 80;

        if (args.Length == 0)
            // 如果没有输入参数，则用当前主机作为缺省参数. 
            host = Dns.GetHostName();
        else
            host = args[0];

        string result = SocketSendReceive(host, port);
        Console.WriteLine(result);
    }
}

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二、使用 WebClient 类下载

using System;
using System.ComponentModel;
using System.Net;
using System.Windows.Forms;

namespace WebClientDownload
{
    public partial class Form1 : Form
    {
        private bool isBusy;
        private WebClient client;

        public Form1()
        {
            InitializeComponent();
            client = new WebClient();

            // 订阅下载完成事件.
            client.DownloadFileCompleted += client_DownloadFileCompleted;
            // 订阅下载进度事件.
            client.DownloadProgressChanged += client_DownloadProgressChanged;
        }

        private void downloadButton_Click(object sender, EventArgs e)
        {
            // 如果正在下载中, 则取消下载.
            if (isBusy)
            {
                client.CancelAsync();
                isBusy = false;
                downloadButton.Text = "下载";
            }
            // 否则，下载
            else
            {
                try
                {
                    Uri uri = new Uri(urlTextBox.Text);
                    downloadProgressBar.Value = 0;
                    if (urlTextBox.Text.EndsWith("/"))
                        client.DownloadFileAsync(uri, "localfile.htm");
                    else
                        client.DownloadFileAsync(uri, urlTextBox.Text.Substring(urlTextBox.Text.LastIndexOf("/") + 1));
                    downloadButton.Text = "取消";
                    isBusy = true;
                }
                catch (UriFormatException ex)
                {
                    MessageBox.Show(ex.Message);
                }
            }
        }

        // 显示下载是否完成的消息.
        private void client_DownloadFileCompleted(object sender, AsyncCompletedEventArgs e)
        {
            isBusy = false;
            downloadButton.Text = "下载";
            if (e.Error == null)
                MessageBox.Show("下载完成");
            else
                MessageBox.Show("下载未能完成: " + e.Error.Message);
        }

        // 刷新进度条
        private void client_DownloadProgressChanged(object sender, DownloadProgressChangedEventArgs e)
        {
            downloadProgressBar.Value = e.ProgressPercentage;
        }
    }
}

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