C#实现一个最简单的HTTP服务器
简介
本文用C#实现了一个最简单的HTTP服务器类，你可以将它嵌入到自己的项目中，或者也可以阅读代码来学习关于HTTP协议的知识。
背景
高性能的WEB应用一般都架设在强大的WEB服务器上，例如IIS, Apache, 和Tomcat。然而，HTML是非常灵活的UI标记语言，也就是说任何应用和后端服务都可以提供HTML的生成支持。在这个小小的例子中，像IIS,、Apache这样的服务器消耗的资源太大了，我们需要自己实现一个简单的HTTP服务器，将它嵌入到我们的应用中用来处理WEB请求。我们仅需要一个类就可以实现了，很简单。
代码实现
首先我们来回顾一下如何使用类，然后我们再来分析实现的具体细节。这里我们创建了一个继承于HttpServer的类，并实现了handleGETRequest 和handlePOSTRequest 这两个抽象方法：
public class MyHttpServer : HttpServer {
public MyHttpServer(intport):base(port)
{
}
public override void handleGETRequest(HttpProcessor p) {
Console.WriteLine("request: {0}", p.http_url);
p.writeSuccess();
p.outputStream.WriteLine("<html><body><h1>test server</h1>");
p.outputStream.WriteLine("Current Time: " + DateTime.Now.ToString());
p.outputStream.WriteLine("url : {0}", p.http_url);
p.outputStream.WriteLine("<form method=post action=/form>");
p.outputStream.WriteLine("<input type=text name=foo value=foovalue>");
p.outputStream.WriteLine("<input type=submit name=bar value=barvalue>");
p.outputStream.WriteLine("</form>");
}
public override void handlePOSTRequest(HttpProcessor p, StreamReader inputData) {
Console.WriteLine("POST request: {0}", p.http_url);
stringdata = inputData.ReadToEnd();
p.outputStream.WriteLine("<html><body><h1>test server</h1>");
p.outputStream.WriteLine("<a href=/test>return</a><p>");
p.outputStream.WriteLine("postbody: <pre>{0}</pre>", data);
}
}
当开始处理一个简单的请求时，我们就需要单独启动一个线程来监听一个端口，比如8080端口：
HttpServer httpServer = new MyHttpServer(8080); Thread thread = new Thread(newThreadStart(httpServer.listen)); thread.Start();
如果你编译运行这个项目，你会在浏览器http://localhost:8080地址下看到页面上生成的示例内容。让我们来简单看一下这个HTTP服务器引擎是怎么实现的。
这个WEB服务器由两个组件构成，一个是负责启动TcpListener来监听指定端口的HttpServer类，并且用AcceptTcpClient()方法循环处理TCP连接请求，这是处理TCP连接的第一步。然后请求到达“已指定“的端口，接着就会创建一对新的端口，用来初始化客户端到服务器端的TCP连接。这对端口便是TcpClient的session，这样就可以保持我们的主端口可以继续接收新的连接请求。从下面的代码中我们可以看到，每一次监听程序都会创建一个新的TcpClien，HttpServer类又会创建一个新的HttpProcessor，然后启动一个线程来操作。HttpServer类中还包含两个抽象方法，你必须实现这两个方法。
public abstract class HttpServer {
protected int port;
TcpListener listener;
boolis_active = true;
publicHttpServer(intport)
{
this.port = port;
}
public void listen() {
listener = newTcpListener(port);
listener.Start();
while(is_active)
{
TcpClient s = listener.AcceptTcpClient();
HttpProcessor processor = newHttpProcessor(s,
this);
Thread thread = newThread(newThreadStart(processor.process));
thread.Start();
Thread.Sleep(1);
}
}
public abstract void handleGETRequest(HttpProcessor p);
public abstract void handlePOSTRequest(HttpProcessor p, StreamReader inputData);
}
这样，一个新的tcp连接就在自己的线程中被HttpProcessor处理了，HttpProcessor的工作就是正确解析HTTP头，并且控制正确实现的抽象方法。下面我们来看看HTTP头的处理过程，HTTP请求的第一行代码如下：
GET /myurl HTTP/1.0
在设置完process()的输入和输出后，HttpProcessor就会调用parseRequest()方法。
public void parseRequest() {
String request = inputStream.ReadLine();
string[] tokens = request.Split(' ');
if(tokens.Length != 3) {
throw new Exception("invalid http request line");
}
http_method = tokens[0].ToUpper();
http_url = tokens[1];
http_protocol_versionstring = tokens[2];
Console.WriteLine("starting: " + request);
}
HTTP请求由3部分组成，所以我们只需要用string.Split()方法将它们分割成3部分即可，接下来就是接收和解析来自客户端的HTTP头信息，头信息中的每一行数据是以Key-Value（键-值）形式保存，空行表示HTTP头信息结束标志，我们代码中用readHeaders方法来读取HTTP头信息：
public void readHeaders() {
Console.WriteLine("readHeaders()");
String line;
while((line = inputStream.ReadLine()) != null)
{
if(line.Equals(""))
{
Console.WriteLine("got headers");
return;
}
intseparator = line.IndexOf(':');
if(separator == -1) {
throw new Exception("invalid http header line: " + line);
}
String name = line.Substring(0, separator);
intpos = separator + 1;
while((pos < line.Length) && (line[pos] == '
'))
{
pos++;// 过滤掉所有空格
}
string value = line.Substring(pos, line.Length - pos);
Console.WriteLine("header: {0}:{1}",name,value);
httpHeaders[name] = value;
}
}
到这里，我们已经了解了如何处理简单的GET和POST请求，它们分别被分配给正确的handler处理程序。在本例中，发送数据的时候有一个棘手的问题需要处理，那就是请求头信息中包含发送数据的长度信息content-length，当我们希望子类HttpServer中的handlePOSTRequest方法能够正确处理数据时，我们需要将数据长度content-length信息一起放入数据流中，否则发送端会因为等待永远不可能到达的数据和阻塞等待。我们用了一种看起来不那么优雅但非常有效的方法来处理这种情况，即将数据发送给POST处理方法前先把数据读入到MemoryStream中。这种做法不太理想，原因如下：如果发送的数据很大，甚至是上传一个文件，那么我们将这些数据缓存在内存就不那么合适甚至是不可能的。理想的方法是限制post的长度，比如我们可以将数据长度限制为10MB。
这个简易版HTTP服务器另一个简化的地方就是content-type的返回值，在HTTP协议中，服务器总是会将数据的MIME-Type发送给客户端，告诉客户端自己需要接收什么类型的数据。在writeSuccess()方法中，我们看到，服务器总是发送text/html类型，如果你需要加入其他的类型，你可以扩展这个方法。
完整代码：
using System;
using System.Collections;
using System.IO;
using System.Net;
using System.Net.Sockets;
using System.Threading;
namespace Bend.Util {
public class HttpProcessor {
public TcpClient socket;
public HttpServer srv;
private Stream inputStream;
public StreamWriter outputStream;
public String http_method;
public String http_url;
public String http_protocol_versionstring;
public Hashtable httpHeaders = new Hashtable();
private static int MAX_POST_SIZE = 10 * 1024 * 1024; // 10MB
public HttpProcessor(TcpClient s, HttpServer srv) {
this.socket = s;
this.srv = srv;
}
private string streamReadLine(Stream inputStream) {
int next_char;
string data = "";
while (true) {
next_char = inputStream.ReadByte();
if (next_char == '\n') { break; }
if (next_char == '\r') { continue; }
if (next_char == -1) { Thread.Sleep(1); continue; };
data += Convert.ToChar(next_char);
}
return data;
}
public void process() {
// we can't use a StreamReader for input, because it buffers up extra data on us inside it's
// "processed" view of the world, and we want the data raw after the headers
inputStream = new BufferedStream(socket.GetStream());
// we probably shouldn't be using a streamwriter for all output from handlers either
outputStream = new StreamWriter(new BufferedStream(socket.GetStream()));
try {
parseRequest();
readHeaders();
if (http_method.Equals("GET")) {
handleGETRequest();
} else if (http_method.Equals("POST")) {
handlePOSTRequest();
}
} catch (Exception e) {
Console.WriteLine("Exception: " + e.ToString());
writeFailure();
}
outputStream.Flush();
// bs.Flush(); // flush any remaining output
inputStream = null; outputStream = null; // bs = null;
socket.Close();
}
public void parseRequest() {
String request = streamReadLine(inputStream);
string[] tokens = request.Split(' ');
if (tokens.Length != 3) {
throw new Exception("invalid http request line");
}
http_method = tokens[0].ToUpper();
http_url = tokens[1];
http_protocol_versionstring = tokens[2];
Console.WriteLine("starting: " + request);
}
public void readHeaders() {
Console.WriteLine("readHeaders()");
String line;
while ((line = streamReadLine(inputStream)) != null) {
if (line.Equals("")) {
Console.WriteLine("got headers");
return;
}
int separator = line.IndexOf(':');
if (separator == -1) {
throw new Exception("invalid http header line: " + line);
}
String name = line.Substring(0, separator);
int pos = separator + 1;
while ((pos < line.Length) && (line[pos] == ' ')) {
pos++; // strip any spaces
}
string value = line.Substring(pos, line.Length - pos);
Console.WriteLine("header: {0}:{1}",name,value);
httpHeaders[name] = value;
}
}
public void handleGETRequest() {
srv.handleGETRequest(this);
}
private const int BUF_SIZE = 4096;
public void handlePOSTRequest() {
// this post data processing just reads everything into a memory stream.
// this is fine for smallish things, but for large stuff we should really
// hand an input stream to the request processor. However, the input stream
// we hand him needs to let him see the "end of the stream" at this content
// length, because otherwise he won't know when he's seen it all!
Console.WriteLine("get post data start");
int content_len = 0;
MemoryStream ms = new MemoryStream();
if (this.httpHeaders.ContainsKey("Content-Length")) {
content_len = Convert.ToInt32(this.httpHeaders["Content-Length"]);
if (content_len > MAX_POST_SIZE) {
throw new Exception(
String.Format("POST Content-Length({0}) too big for this simple server",
content_len));
}
byte[] buf = new byte[BUF_SIZE];
int to_read = content_len;
while (to_read > 0) {
Console.WriteLine("starting Read, to_read={0}",to_read);
int numread = this.inputStream.Read(buf, 0, Math.Min(BUF_SIZE, to_read));
Console.WriteLine("read finished, numread={0}", numread);
if (numread == 0) {
if (to_read == 0) {
break;
} else {
throw new Exception("client disconnected during post");
}
}
to_read -= numread;
ms.Write(buf, 0, numread);
}
ms.Seek(0, SeekOrigin.Begin);
}
Console.WriteLine("get post data end");
srv.handlePOSTRequest(this, new StreamReader(ms));
}
public void writeSuccess() {
outputStream.WriteLine("HTTP/1.0 200 OK");
outputStream.WriteLine("Content-Type: text/html;charset=utf-8");
outputStream.WriteLine("Connection: close");
outputStream.WriteLine("");
}
public void writeFailure() {
outputStream.WriteLine("HTTP/1.0 404 File not found");
outputStream.WriteLine("Connection: close");
outputStream.WriteLine("");
}
}
public abstract class HttpServer {
protected int port;
TcpListener listener;
bool is_active = true;
public HttpServer(int port) {
this.port = port;
}
public void listen() {
listener = new TcpListener(port);
listener.Start();
while (is_active) {
TcpClient s = listener.AcceptTcpClient();
HttpProcessor processor = new HttpProcessor(s, this);
Thread thread = new Thread(new ThreadStart(processor.process));
thread.Start();
Thread.Sleep(1);
}
}
public abstract void handleGETRequest(HttpProcessor p);
public abstract void handlePOSTRequest(HttpProcessor p, StreamReader inputData);
}
public class MyHttpServer : HttpServer {
public MyHttpServer(int port)
: base(port) {
}
public override void handleGETRequest(HttpProcessor p) {
Console.WriteLine("request: {0}", p.http_url);
p.writeSuccess();
p.outputStream.WriteLine("<html><body><h1>test server</h1>");
p.outputStream.WriteLine("Current Time: " + DateTime.Now.ToString());
p.outputStream.WriteLine("url : {0}", p.http_url);
p.outputStream.WriteLine("<form method=post action=/form>");
p.outputStream.WriteLine("<input type=text name=foo value=foovalue>");
p.outputStream.WriteLine("<input type=submit name=bar value=barvalue>");
p.outputStream.WriteLine("</form>");
}
public override void handlePOSTRequest(HttpProcessor p, StreamReader inputData) {
Console.WriteLine("POST request: {0}", p.http_url);
string data = inputData.ReadToEnd();
p.outputStream.WriteLine("<html><body><h1>test server</h1>");
p.outputStream.WriteLine("<a href=/test>return</a><p>");
p.outputStream.WriteLine("postbody: <pre>{0}</pre>", data);
}
}
public class TestMain {
public static int Main(String[] args) {
HttpServer httpServer;
if (args.GetLength(0) > 0) {
httpServer = new MyHttpServer(Convert.ToInt16(args[0]));
} else {
httpServer = new MyHttpServer(8080);
}
Thread thread = new Thread(new ThreadStart(httpServer.listen));
thread.Start();
return 0;
}
}
}
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