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利用HttpListener创建简单的HTTP服务

2016-04-07 18:36 519 查看
using System;
using System.Collections.Generic;
using System.IO;
using System.IO.Compression;
using System.Linq;
using System.Net;
using System.Reflection;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading;
using System.Threading.Tasks;
public class HttpServer : IDisposable
{
private const string NotFoundResponse = "<!doctype html><html><body>Resource not found</body></html>";
private readonly HttpListener httpListener;
private readonly CancellationTokenSource cts = new CancellationTokenSource();
private readonly string prefixPath;

private Task processingTask;

public HttpServer(string listenerUriPrefix)
{
this.prefixPath = ParsePrefixPath(listenerUriPrefix);
this.httpListener = new HttpListener();
this.httpListener.Prefixes.Add(listenerUriPrefix);
}

private static string ParsePrefixPath(string listenerUriPrefix)
{
var match = Regex.Match(listenerUriPrefix, @"http://(?:[^/]*)(?:\:\d+)?/(.*)");
if (match.Success)
{
return match.Groups[1].Value.ToLowerInvariant();
}
else
{
return string.Empty;
}
}

public void Start()
{
this.httpListener.Start();
this.processingTask = Task.Factory.StartNew(async () => await ProcessRequests(), TaskCreationOptions.LongRunning);
}

private async Task ProcessRequests()
{
while (!this.cts.IsCancellationRequested)
{
try
{
var context = await this.httpListener.GetContextAsync();
try
{
await ProcessRequest(context).ConfigureAwait(false);
context.Response.Close();
}
catch (Exception ex)
{
context.Response.StatusCode = 500;
context.Response.StatusDescription = "Internal Server Error";
context.Response.Close();
Console.WriteLine("Error processing HTTP request\n{0}", ex);
}
}
catch (ObjectDisposedException ex)
{
if ((ex.ObjectName == this.httpListener.GetType().FullName) && (this.httpListener.IsListening == false))
{
return; // listener is closed/disposed
}
Console.WriteLine("Error processing HTTP request\n{0}", ex);
}
catch (Exception ex)
{
HttpListenerException httpException = ex as HttpListenerException;
if (httpException == null || httpException.ErrorCode != 995)// IO operation aborted
{
Console.WriteLine("Error processing HTTP request\n{0}", ex);
}
}
}
}

private Task ProcessRequest(HttpListenerContext context)
{
if (context.Request.HttpMethod.ToUpperInvariant() != "GET")
{
return WriteNotFound(context);
}

var urlPath = context.Request.RawUrl.Substring(this.prefixPath.Length)
.ToLowerInvariant();

switch (urlPath)
{
case "/":
if (!context.Request.Url.ToString().EndsWith("/"))
{
context.Response.Redirect(context.Request.Url + "/");
context.Response.Close();
return Task.FromResult(0);
}
else
{
return WriteString(context, "Hello World!", "text/plain");
}
case "/favicon.ico":
return WriteFavIcon(context);
case "/ping":
return WritePong(context);
}
return WriteNotFound(context);
}

private static Task WritePong(HttpListenerContext context)
{
return WriteString(context, "pong", "text/plain");
}

private static async Task WriteFavIcon(HttpListenerContext context)
{
context.Response.ContentType = "image/png";
context.Response.StatusCode = 200;
context.Response.StatusDescription = "OK";
using (var stream = File.Open("icon.png", FileMode.Open))
{
var output = context.Response.OutputStream;
await stream.CopyToAsync(output);
}
}

private static Task WriteNotFound(HttpListenerContext context)
{
return WriteString(context, NotFoundResponse, "text/plain", 404, "NOT FOUND");
}

private static async Task WriteString(HttpListenerContext context, string data, string contentType,
int httpStatus = 200, string httpStatusDescription = "OK")
{
AddCORSHeaders(context.Response);
AddNoCacheHeaders(context.Response);

context.Response.ContentType = contentType;
context.Response.StatusCode = httpStatus;
context.Response.StatusDescription = httpStatusDescription;

var acceptsGzip = AcceptsGzip(context.Request);
if (!acceptsGzip)
{
using (var writer = new StreamWriter(context.Response.OutputStream, Encoding.UTF8, 4096, true))
{
await writer.WriteAsync(data).ConfigureAwait(false);
}
}
else
{
context.Response.AddHeader("Content-Encoding", "gzip");
using (GZipStream gzip = new GZipStream(context.Response.OutputStream, CompressionMode.Compress, true))
using (var writer = new StreamWriter(gzip, Encoding.UTF8, 4096, true))
{
await writer.WriteAsync(data).ConfigureAwait(false);
}
}
}

private static bool AcceptsGzip(HttpListenerRequest request)
{
string encoding = request.Headers["Accept-Encoding"];
if (string.IsNullOrEmpty(encoding))
{
return false;
}

return encoding.Contains("gzip");
}

private static void AddNoCacheHeaders(HttpListenerResponse response)
{
response.Headers.Add("Cache-Control", "no-cache, no-store, must-revalidate");
response.Headers.Add("Pragma", "no-cache");
response.Headers.Add("Expires", "0");
}

private static void AddCORSHeaders(HttpListenerResponse response)
{
response.Headers.Add("Access-Control-Allow-Origin", "*");
response.Headers.Add("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");
}

private void Stop()
{
cts.Cancel();
if (processingTask != null && !processingTask.IsCompleted)
{
processingTask.Wait();
}
if (this.httpListener.IsListening)
{
this.httpListener.Stop();
this.httpListener.Prefixes.Clear();
}
}

public void Dispose()
{
this.Stop();
this.httpListener.Close();
using (this.cts) { }
using (this.httpListener) { }
}
}
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