例如,使用这篇文章,我编写了检查 200 个代理的代码。套接字的超时时间为 2 秒。一切正常,但问题是代码 #1需要超过 2 分钟才能检查 200 个代理,限制为 2 秒超时。但是使用Code #2检查 200 个代理需要 2 秒,使用Code #2检查 1000 个代理也需要 2 秒。
代码 #1使用线程池。
代码 #1打开proxyCount
套接字,进入休眠状态 2 秒,然后检查成功。正好需要 2 秒。
那么代码 #1中的问题在哪里?为什么至少有 20 个线程的 ThreadPool 比没有线程的要慢得多?
代码 #1
int proxyCount = 200;
CountdownEvent cde = new CountdownEvent(proxyCount);
private void RefreshProxyIPs(object obj)
{
int workerThreads, ioThreads;
ThreadPool.GetMinThreads(out workerThreads, out ioThreads);
ThreadPool.SetMinThreads(20, ioThreads);
var proxies = GetServersIPs(proxyCount);
watch.Start();
for (int i = 0; i < proxyCount; i++)
{
var proxy = proxies[i];
ThreadPool.QueueUserWorkItem(CheckProxy, new IPEndPoint(IPAddress.Parse(proxy.IpAddress), proxy.Port));
}
cde.Wait();
cde.Dispose();
watch.Stop();
}
private List<IPEndPoint> list = new List<IPEndPoint>();
private void CheckProxy(object o)
{
var proxy = o as IPEndPoint;
using (var socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp))
{
var asyncResult = socket.BeginConnect(proxy.Address, proxy.Port, null, null);
if (asyncResult.AsyncWaitHandle.WaitOne(2000))
{
try
{
socket.EndConnect(asyncResult);
}
catch (SocketException)
{
}
catch (ObjectDisposedException)
{
}
}
if (socket.Connected)
{
list.Add(proxy);
socket.Close();
}
}
cde.Signal();
}
代码 #2
int proxyCount = 200;
var sockets = new Socket[proxyCount];
var socketsResults = new IAsyncResult[proxyCount];
var proxies = GetServersIPs(proxyCount);
for (int i = 0; i < proxyCount; i++)
{
var proxy = proxies[i];
sockets[i] = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
socketsResults[i] = sockets[i].BeginConnect(IPAddress.Parse(proxy.IpAddress), proxy.Port, null, proxy);
}
Thread.Sleep(2000);
for (int i = 0; i < proxyCount; i++)
{
var success = false;
try
{
if (socketsResults[i].IsCompleted)
{
sockets[i].EndConnect(socketsResults[i]);
success = sockets[i].Connected;
sockets[i].Close();
}
sockets[i].Dispose();
}
catch { }
var proxy = socketsResults[i].AsyncState as Proxy;
if (success) { _validProxies.Add(proxy); }
}