关于HttpWebRequest下载过程中网络连接断开的问题

2011-12-15 04:15:25 524 阅读 AI 写同款 · GEO 优化AI 选题数据监测一键分发 ›

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下载的方法：



            /// <summary>

            /// 下载文件

            /// </summary>

            /// <param name="url">文件路径</param>

            /// <param name="startPos">起始位置</param>

            /// <param name="bytesCount">读取字节数</param>

            /// <returns></returns>

            public byte[] DownLoadFile(string url, int startPos, int bytesCount)

            {

                ServicePointManager.DefaultConnectionLimit = 100;



                System.Net.HttpWebRequest request = (System.Net.HttpWebRequest)System.Net.HttpWebRequest.Create(url);

                request.KeepAlive = false;

                request.AddRange(startPos, startPos + bytesCount - 1); 

                System.Net.WebResponse response =null ;



                try

                {

                    Console.WriteLine("请求数据");

                    response = request.GetResponse();

                }

                catch (WebException wex)

                {

                    Console.WriteLine("请求数据WebException");

                    request.Abort();

                    throw wex;

                }

                catch (Exception ex)

                {

                    Console.WriteLine("请求数据Exception");

                    request.Abort();

                    throw ex;

                }





                try

                {

                    System.IO.Stream receiveStream = response.GetResponseStream();

                    System.IO.BinaryReader readStream = new System.IO.BinaryReader(receiveStream);

                    byte[] buffer = new byte[0];

                    byte[] read = new byte[256];

                    int count = readStream.Read(read, 0, 256);

                    while (count > 0)

                    {

                        Array.Resize<byte>(ref buffer, buffer.Length + count);

                        Array.Copy(read, 0, buffer, buffer.Length - count, count);

                        count = readStream.Read(read, 0, 256);

                    }

                    readStream.Close();

                    return buffer;

                }

                finally

                {

                    response.Close();

                }

            }

        }

调用下载方法的线程：



                    byte[] buffer = null;

                    //当服务器返回的数据长度不等于文件长度时，下载完成

                    while (startPos < FileSize)

                    {

                            string errorInfo = null;

                            try

                            {

                                buffer = HttpDownload.DownLoadFile(url, (int)startPos, blockSize);

                                returnSize = buffer.Length;

                                startPos += returnSize;

                                WriteToFile(buffer);

                                Percent = (int)Math.Floor(startPos * 100.0 / FileSize); 

                            }

                            catch (WebException wex)

                            {

                                errorInfo = "连接失败";

                                Thread.Sleep(3000);

                            }

                            catch (Exception ex)

                            {

                                errorInfo = "连接失败";

                                Thread.Sleep(3000);

                            }

                    }