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;
        }

    }

}

posted @ 2019-11-14 15:16 小y 阅读(24337) 评论(0) 编辑收藏举报

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C#实现一个最简单的HTTP服务器

简介

背景

代码实现

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