使用TcpClient 异步下载网页

最新推荐文章于 2020-12-22 10:20:07 发布

bluedoctor

最新推荐文章于 2020-12-22 10:20:07 发布

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分类专栏： .NET 技术文章标签： string byte encoding html .net buffer

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本文介绍如何利用NetworkStream的BeginRead方法实现异步数据读取，并通过递归调用确保完整下载TCP数据。文章提供了具体代码示例，展示了如何设置HTTP请求头并接收服务器响应。

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使用NetworkStream 的BeginRead方法，要注意的是，必须使用异步结束时候获得的numberOfBytesRead长度，否则可能会有问题。

下面的代码需要递归调用，直到全部下载完成。

myNetworkStream.BeginRead(myReadBuffer, 0, numberOfBytesRead,
new AsyncCallback(myReadCallBack),
myNetworkStream);

详细代码如下：

static void Main(string[] args) { string html = GetHTMLTCP("http://localhost:4169/Default.aspx"); Console.Write(html); Console.Read(); } private static string GetHTMLTCP(string URL) { string strHTML = "";//用来保存获得的HTML代码 TcpClient clientSocket = new TcpClient(); Uri URI = new Uri(URL); clientSocket.Connect(URI.Host, URI.Port); StringBuilder RequestHeaders = new StringBuilder();//用来保存HTML协议头部信息 RequestHeaders.AppendFormat("{0} {1} HTTP/1.1/r/n", "GET"/*此处可填写GET或POST*/, URI.PathAndQuery); RequestHeaders.AppendFormat("Connection:close/r/n"); RequestHeaders.AppendFormat("Host:{0}/r/n", URI.Host); RequestHeaders.AppendFormat("Accept:*/*/r/n"); RequestHeaders.AppendFormat("Accept-Language:zh-cn/r/n"); RequestHeaders.AppendFormat("User-Agent:Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.2; SV1; .NET CLR 1.1.4322; .NET CLR 2.0.50727)/r/n/r/n"); Encoding encoding = Encoding.Default; byte[] request = encoding.GetBytes(RequestHeaders.ToString()); clientSocket.Client.Send(request); //获取要保存的网络流 NetworkStream readStream = clientSocket.GetStream(); //StreamReader sr = new StreamReader(readStream, Encoding.Default); //strHTML = sr.ReadToEnd(); //readStream.Close(); //clientSocket.Close(); //readStream.EndRead(); //return strHTML; //下面的方式为异步接收数据 if (readStream.CanRead) { byte[] buf = new byte[1024]; IAsyncResult result = readStream.BeginRead(buf, 0, buf.Length, new AsyncCallback(myReadCallBack), readStream); } return ""; } public static void myReadCallBack(IAsyncResult ar) { NetworkStream myNetworkStream = (NetworkStream)ar.AsyncState; byte[] myReadBuffer = new byte[1024]; String myCompleteMessage = ""; int numberOfBytesRead; numberOfBytesRead = myNetworkStream.EndRead(ar); if (numberOfBytesRead < 1) return; // message received may be larger than buffer size so loop through until you have it all. while (myNetworkStream.DataAvailable) { //System.Threading.Thread.Sleep(10); myNetworkStream.BeginRead(myReadBuffer, 0, numberOfBytesRead, new AsyncCallback(myReadCallBack), myNetworkStream); //myCompleteMessage = //String.Concat(myCompleteMessage, Encoding.Default.GetString(myReadBuffer, 0, numberOfBytesRead)); myCompleteMessage = Encoding.Default.GetString(myReadBuffer, 0, numberOfBytesRead); // Print out the received message to the console. Console.WriteLine(myCompleteMessage); } }