c#使用Socket获取网页(含自动跳转, 解压网页)

using System;
using System.IO;
using System.IO.Compression;
using System.Net.Sockets;
using System.Text;
using System.Text.RegularExpressions;
public class GetPageWithSocket
{
    /// <summary>
    /// 使用socket得到网页html
    /// </summary>
    /// <param name="strUrl">网页url</param>
    /// <returns>网页html代码</returns>
    public string GetHtml(string strUrl)
    {

        bool hasRelocated = false;
        string strHost = GetHost(strUrl);
        string strGetHeader = "GET " + GetRelativeUrl(strUrl) + " HTTP/1.1\r\nHost: " + strHost + "\r\nConnection: Close\r\n\r\n";
        byte[] getBytes = Encoding.ASCII.GetBytes(strGetHeader);
        try
        {
            int iTotalCount;
            byte[] responseBytes = GetHtmlOriginByte(strHost, getBytes, out iTotalCount); //得到网页
            string strResponse = Encoding.UTF8.GetString(responseBytes, 0, iTotalCount);
            hasRelocated = HasRelocated(ref strResponse);
            if (!hasRelocated) //如果没跳转则转化字符后返回
            {
                int iStart = FindBodyStartPosition(responseBytes);
                //总长度不再计算头http头部了
                iTotalCount -= iStart;
                int iIndex = strResponse.IndexOf("\r\n\r\n");
                string strHeader = strResponse.Substring(0, iIndex);//头部
                DecompressWebPage(ref responseBytes, ref iTotalCount, strHeader, iStart);
                //转码
                strResponse = DecodeWebStringByHttpHeader(responseBytes, iTotalCount, strHeader);
                strResponse = DecodeWebStringByHtmlPageInfo(responseBytes, iTotalCount, strResponse);
            }
            return strResponse;
        }
        catch (System.Exception ex)
        {
            return "";
        }
    }
    /// <summary>
    /// 得到网页原始字节数组
    /// </summary>
    /// <param name="strHost">主机头</param>
    /// <param name="getBytes">Get字符串的字节数组形式</param>
    /// <param name="iTotalCount">接受的字节数</param>
    /// <returns>原始网页字节数组</returns>
    private byte[] GetHtmlOriginByte(string strHost, byte[] getBytes, out int iTotalCount)
    {
        int iReponseByteSize = 400 * 1024;
        Socket socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
        socket.Connect(strHost, 80);
        socket.Send(getBytes);
        byte[] buffer = new byte[256];
        byte[] responseBytes = new byte[iReponseByteSize];
        int iNumber = socket.Receive(buffer, buffer.Length, SocketFlags.None);
        iTotalCount = iNumber;
        buffer.CopyTo(responseBytes, 0);
        while (iNumber > 0)
        {
            iNumber = socket.Receive(buffer, buffer.Length, SocketFlags.None);
            if (iTotalCount + iNumber >= responseBytes.Length)
            {
                //重新生成个更大的数组
                byte[] temp = new byte[responseBytes.Length * 2];
                //原数据copy到新数组中
                responseBytes.CopyTo(temp, 0);
                buffer.CopyTo(temp, iTotalCount - 1);
                responseBytes = temp; //引用变更
            }
            else
            {
                buffer.CopyTo(responseBytes, iTotalCount - 1);
            }
            iTotalCount += iNumber; //索引位置增加
        }
        return responseBytes;
    }
    /// <summary>
    /// 解压网页
    /// </summary>
    /// <param name="responseBytes">网页字节数组含http头</param>
    /// <param name="iTotalCount">数组长度</param>
    /// <param name="strHeader">Http头字符串</param>
    /// <param name="iStart">网页正文开始位置</param>
    private void DecompressWebPage(ref byte[] responseBytes, ref int iTotalCount, string strHeader, int iStart)
    {
        byte[] szSwapBuffer = new byte[iTotalCount];
        Array.Copy(responseBytes, iStart, szSwapBuffer, 0, iTotalCount);
        Regex regZip = new Regex(@"Content-Encoding:\s+gzip[^\n]*\r\n", RegexOptions.IgnoreCase);

        if (regZip.IsMatch(strHeader))
        {
            responseBytes = Decompress(szSwapBuffer);
            iTotalCount = responseBytes.Length; //解压后长度变了
        }
        else
        {
            responseBytes = szSwapBuffer;
        }
    }
    /// <summary>
    /// 根据网页meta标记里面的字符编码解析字符串
    /// </summary>
    /// <param name="responseBytes">网页内容字节数组(除http头以外的内容)</param>
    /// <param name="iTotalCount">网页内容字节数组长度</param>
    /// <param name="strResponse">网页内容字符串, 可能已经根据其它转码要求转换过的字符串</param>
    /// <returns>转好的字符串</returns>
    private string DecodeWebStringByHtmlPageInfo(byte[] responseBytes, int iTotalCount, string strResponse)
    {
        Regex regGB2312 = new Regex(@"<meta[^>]+Content-Type[^>]+gb2312[^>]*>", RegexOptions.IgnoreCase);
        Regex regGBK = new Regex(@"<meta[^>]+Content-Type[^>]+gbk[^>]*>", RegexOptions.IgnoreCase);
        Regex regBig5 = new Regex(@"<meta[^>]+Content-Type[^>]+Big5[^>]*>", RegexOptions.IgnoreCase);
        if (regGB2312.IsMatch(strResponse) || regGBK.IsMatch(strResponse))
            strResponse = Encoding.GetEncoding("GBK").GetString(responseBytes, 0, iTotalCount);
        if (regBig5.IsMatch(strResponse))
            strResponse = Encoding.GetEncoding("Big5").GetString(responseBytes, 0, iTotalCount);
        return strResponse;
    }
    /// <summary>
    /// 根据Http头标记里面的字符编码解析字符串
    /// </summary>
    /// <param name="responseBytes">网页内容字节数组(除http头以外的内容)</param>
    /// <param name="iTotalCount">网页内容字节数组长度</param>
    /// <param name="strHeader">http头的字符串</param>
    /// <returns>转好的字符串</returns>
    private string DecodeWebStringByHttpHeader(byte[] responseBytes, int iTotalCount, string strHeader)
    {
        string strResponse = "";
        if (strHeader.Contains("charset=GBK") || strHeader.Contains("charset=gb2312"))
        {
            strResponse = Encoding.GetEncoding("GBK").GetString(responseBytes, 0, iTotalCount);
        }
        else
            strResponse = Encoding.UTF8.GetString(responseBytes, 0, iTotalCount);
        return strResponse;
    }
    /// <summary>
    /// 是否已跳转
    /// </summary>
    /// <param name="strResponse">http响应字符串</param>
    /// <returns>bool值 是否跳转</returns>
    private bool HasRelocated(ref string strResponse)
    {
        bool hasRelocated = false;
        int iIndex = strResponse.IndexOf("\r\n\r\n");
        string strHeader = strResponse.Substring(0, iIndex);//头部
        if (strResponse.StartsWith("HTTP/1.1 302") || strResponse.StartsWith("HTTP/1.1 301"))//跳转
        {
            int iStart = strHeader.IndexOf("\r\nLocation: ");
            string strRelocateUrl = strHeader.Substring(iStart + "\r\nLocation: ".Length);
            int iEnd = strRelocateUrl.IndexOf("\r\n");
            strRelocateUrl = strRelocateUrl.Substring(0, iEnd);
            strResponse = GetHtml(strRelocateUrl); //递归的获取
            hasRelocated = true;
        }
        return hasRelocated;
    }
    /// <summary>
    /// 查找html开始部分(去除了html头)\r\n\r\n后面第一个byte的位置
    /// </summary>
    /// <param name="szHtmlBuffer">接受到的byte数组</param>
    /// <returns>第一个byte位置</returns>
    private int FindBodyStartPosition(byte[] szHtmlBuffer)
    {
        for (int i = 0; i < szHtmlBuffer.Length - 3; ++i)
        {
            if (szHtmlBuffer[i] == 13 && szHtmlBuffer[i + 1] == 10 && szHtmlBuffer[i + 2] == 13 && szHtmlBuffer[i + 3] == 10)
                return i + 4;
        }
        return -1;
    }
    /// <summary>
    /// 得到请求资源的相对路径
    /// </summary>
    /// <param name="strUrl">Url字符串</param>
    /// <returns>url的相对路径</returns>
    private string GetRelativeUrl(string strUrl)
    {
        int iIndex = strUrl.IndexOf(@"//");
        if (iIndex <= 0)
            return "/";
        string strTemp = strUrl.Substring(iIndex + 2);
        iIndex = strTemp.IndexOf(@"/");
        if (iIndex > 0)
            return strTemp.Substring(iIndex);
        else
            return "/";
    }
    /// <summary>
    /// 根据Url得到host
    /// </summary>
    /// <param name="strUrl">url字符串</param>
    /// <returns>host字符串</returns>
    private string GetHost(string strUrl)
    {
        int iIndex = strUrl.IndexOf(@"//");
        if (iIndex <= 0)
            return "";
        string strTemp = strUrl.Substring(iIndex + 2);
        iIndex = strTemp.IndexOf(@"/");
        if (iIndex > 0)
            return strTemp.Substring(0, iIndex);
        else
            return strTemp;
    }
    /// <summary>
    /// 解压gzip网页
    /// </summary>
    /// <param name="szSource">压缩过的字符串字节数组</param>
    /// <returns>解压后的字节数组</returns>
    private byte[] Decompress(byte[] szSource)
    {
        MemoryStream msSource = new MemoryStream(szSource);
        //DeflateStream  也可以这儿
        GZipStream stream = new GZipStream(msSource, CompressionMode.Decompress);
        byte[] szTotal = new byte[40 * 1024];
        long lTotal = 0;
        byte[] buffer = new byte[8];
        int iCount = 0;
        do
        {
            iCount = stream.Read(buffer, 0, 8);
            if (szTotal.Length <= lTotal + iCount) //放大数组
            {
                byte[] temp = new byte[szTotal.Length * 10];
                szTotal.CopyTo(temp, 0);
                szTotal = temp;
            }
            buffer.CopyTo(szTotal, lTotal);
            lTotal += iCount;
        } while (iCount != 0);
        byte[] szDest = new byte[lTotal];
        Array.Copy(szTotal, 0, szDest, 0, lTotal);
        return szDest;
    }

    public static void Method_11()
        {
            Console.Write("请输入网址:");
            string strUrl = Console.ReadLine();
            string strResponse = new GetPageWithSocket().GetHtml(strUrl);
            Console.WriteLine(strResponse);
            Console.ReadKey();
        }
}