“NanoHttpd微型服务器”使用及源码阅读

“NanoHttpd微型服务器”使用及源码阅读

偶然返现NanoHttpd,仅仅一个Java文件,可在嵌入式设备(例:Android手机)中启动一个本地服务器,接收客户端本地部分请求。
认真学习了其源码实现,这里按照我的学习顺序写了一篇简单的文章(算是学习笔记吧):

  • 了解官方描述
  • 写个Demo使用一下(Android中本地代理,播放Sdcard中的m3u8)
  • 最后学习其源码实现

NanoHttpd GitHub地址:
https://github.com/NanoHttpd/nanohttpd

首先看一下官方相关描述。

NanoHttpd 官方描述

Tiny, easily embeddable HTTP server in Java.
微小的,轻量级适合嵌入式设备的Java Http服务器;
NanoHTTPD is a light-weight HTTP server designed for embedding in other applications, released under a Modified BSD licence.
NanoHTTPD是一个轻量级的、为嵌入式设备应用设计的HTTP服务器,遵循修订后的BSD许可协议。

Core

  • Only one Java file, providing HTTP 1.1 support.

仅一个Java文件,支持Http 1.1

  • No fixed config files, logging, authorization etc. (Implement by yourself if you need them. Errors are passed to java.util.logging, though.)

没有固定的配置文件、日志系统、授权等等(如果你有需要需自己实现。工程中的日志输出,通过java.util.logging实现的)

  • Support for HTTPS (SSL).

支持Https

  • Basic support for cookies.

支持cookies

  • Supports parameter parsing of GET and POST methods.

支持POST和GET 参数请求

  • Some built-in support for HEAD, POST and DELETE requests. You can easily implement/customize any HTTP method, though.

内置支持HEAD、POST、DELETE请求,你可以方便的实现或自定义任何HTTP方法请求。

  • Supports file upload. Uses memory for small uploads, temp files for large ones.

支持文件上传。小文件上传使用内存缓存,大文件使用临时文件缓存。

  • Never caches anything.

不缓存任何内容

  • Does not limit bandwidth, request time or simultaneous connections by default.
  • 默认不限制带宽、请求时间 和 最大请求量
  • All header names are converted to lower case so they don't vary between browsers/clients.

所有Header 名都被转换为小写,因此不会因客户端或浏览器的不同而有所差别

  • Persistent connections (Connection "keep-alive") support allowing multiple requests to be served over a single socket connection.

支持一个socket连接服务多个长连接请求。

一、Android 本地代理方式播放 Sdcard中的m3u8视频

为了学习NanoHttpd,做了一个简单Demo:Android 本地代理方式播放 Sdcard中的m3u8视频

Demo实现下载

Android 本地代理方式播放 Sdcard中的m3u8视频(使用的NanoHttpd 版本为 2.3.1

NanoHttpd 2.3.1版本下载

实现效果如下图所示:

在这里插入图片描述

NanoHttpd的使用,使 “本地代理方式播放Android Sdcard中的m3u8视频” Demo实现变得很简单,这里不做具体介绍,有兴趣的朋友可以自行下载了解。

下边来主要来跟踪学习NanoHttpd的源码...

二、NanoHttpd源码跟踪学习

注:基于 NanoHttpd 2.3.1版本
NanoHttpd 2.3.1版本下载

NanoHTTPD大概的处理流程是:

  • 开启一个服务端线程,绑定对应的端口,调用 ServerSocket.accept()方法进入等待状态
  • 每个客户端连接均开启一个线程,执行ClientHandler.run()方法
  • 客户端线程中,创建一个HTTPSession会话。执行HTTPSession.execute()
  • HTTPSession.execute() 中会完成 uri, method, headers, parms, files 的解析,并调用方法
// 自定义服务器时,亦需要重载该方法
// 该方法传入参数中,已解析出客户端请求的所有数据,重载该方法进行相应的业务处理
HTTPSession.serve(String uri, Method method, Map<String, String> headers, Map<String, String> parms, Map<String, String> files)
  • 组织Response数据,并调用ChunkedOutputStream.send(outputStream)返回给客户端

建议:对于Http request、response 数据组织形式不是很了解的同学,建议自己了解后再阅读NanoHTTPD源码。 也可参考我的另一篇文章:Http请求数据格式

NanoHTTPD.start

从服务器启动开始学习...

/**
 * Start the server. 启动服务器
 *
 * @param timeout timeout to use for socket connections. 超时时间
 * @param daemon  start the thread daemon or not. 守护线程
 * @throws IOException if the socket is in use.
 */
public void start(final int timeout, boolean daemon) throws IOException {
    // 创建一个ServerSocket
    this.myServerSocket = this.getServerSocketFactory().create();
    this.myServerSocket.setReuseAddress(true);

    // 创建 ServerRunnable
    ServerRunnable serverRunnable = createServerRunnable(timeout);
    // 启动一个线程监听客户端请求
    this.myThread = new Thread(serverRunnable);
    this.myThread.setDaemon(daemon);
    this.myThread.setName("NanoHttpd Main Listener");
    this.myThread.start();
    //
    while (!serverRunnable.hasBinded && serverRunnable.bindException == null) {
        try {
            Thread.sleep(10L);
        } catch (Throwable e) {
            // on android this may not be allowed, that's why we
            // catch throwable the wait should be very short because we are
            // just waiting for the bind of the socket
        }
    }
    if (serverRunnable.bindException != null) {
        throw serverRunnable.bindException;
    }
}

从以上代码中,可以看到:

  • 代码前两行,创建一个ServerSocket
  • 开启一个线程,执行ServerRunnable。这里其实就是服务端启动一个线程,用来监听客户端的请求,具体代码在ServerRunnable中。

ServerRunnable.run()

@Override
public void run() {
    Log.e(TAG, "---run---");
    try {
        // bind
        myServerSocket.bind(hostname != null ? new InetSocketAddress(hostname, myPort) : new InetSocketAddress(myPort));
        hasBinded = true;
    } catch (IOException e) {
        this.bindException = e;
        return;
    }
    Log.e(TAG, "bind ok");
    do {
        try {
            Log.e(TAG, "before accept");
            // 等待客户端连接
            final Socket finalAccept = NanoHTTPD.this.myServerSocket.accept();
            // 设置超时时间
            if (this.timeout > 0) {
                finalAccept.setSoTimeout(this.timeout);
            }
            // 服务端:输入流
            final InputStream inputStream = finalAccept.getInputStream();
            Log.e(TAG, "asyncRunner.exec");
            // 执行客户端 ClientHandler
            NanoHTTPD.this.asyncRunner.exec(createClientHandler(finalAccept, inputStream));
        } catch (IOException e) {
            NanoHTTPD.LOG.log(Level.FINE, "Communication with the client broken", e);
        }
    } while (!NanoHTTPD.this.myServerSocket.isClosed());
}

ServerRunnablerun()方法:

  • 调用 ServerSocket.bind 方法,绑定对应的端口
  • 调用 ServerSocket.accept() 线程进入阻塞等待状态
  • 客户端连接后,会执行createClientHandler(finalAccept, inputStream)创建一个ClientHandler,并开启一个线程,执行其对应的ClientHandler.run()方法
  • 自定义服务器时,重载Response HTTPSession.serve(uri, method, headers, parms, files)方法,进行相应的业务处理
  • 完成处理后,对于

ClientHandler.run()

@Override
public void run() {
    Log.e(TAG, "---run---");
    // 服务端 输出流
    OutputStream outputStream = null;
    try {
        // 服务端的输出流
        outputStream = this.acceptSocket.getOutputStream();
        // 创建临时文件
        TempFileManager tempFileManager = NanoHTTPD.this.tempFileManagerFactory.create();
        // session 会话
        HTTPSession session = new HTTPSession(tempFileManager, this.inputStream, outputStream, this.acceptSocket.getInetAddress());
        // 执行会话
        while (!this.acceptSocket.isClosed()) {
            session.execute();
        }
    } catch (Exception e) {
        // When the socket is closed by the client,
        // we throw our own SocketException
        // to break the "keep alive" loop above. If
        // the exception was anything other
        // than the expected SocketException OR a
        // SocketTimeoutException, print the
        // stacktrace
        if (!(e instanceof SocketException && "NanoHttpd Shutdown".equals(e.getMessage())) && !(e instanceof SocketTimeoutException)) {
            NanoHTTPD.LOG.log(Level.SEVERE, "Communication with the client broken, or an bug in the handler code", e);
        }
    } finally {
        safeClose(outputStream);
        safeClose(this.inputStream);
        safeClose(this.acceptSocket);
        NanoHTTPD.this.asyncRunner.closed(this);
    }
}
  • TempFileManager临时文件是为了缓存客户端Post请求的请求Body数据(如果数据较小,内存缓存;文件较大,缓存到文件中)
  • 创建一个HTTPSession会话,并执行其对应的HTTPSession.execute()方法
  • HTTPSession.execute()中会对客户端的请求进行解析

HTTPSession.execute()


@Override
public void execute() throws IOException {
    Log.e(TAG, "---execute---");
    Response r = null;
    try {
        // Read the first 8192 bytes.
        // The full header should fit in here.
        // Apache's default header limit is 8KB.
        // Do NOT assume that a single read will get the entire header
        // at once!
        // Apache默认header限制8k
        byte[] buf = new byte[HTTPSession.BUFSIZE];
        this.splitbyte = 0;
        this.rlen = 0;
        // 客户端输入流
        int read = -1;
        this.inputStream.mark(HTTPSession.BUFSIZE);
        // 读取8k的数据
        try {
            read = this.inputStream.read(buf, 0, HTTPSession.BUFSIZE);
        } catch (SSLException e) {
            throw e;
        } catch (IOException e) {
            safeClose(this.inputStream);
            safeClose(this.outputStream);
            throw new SocketException("NanoHttpd Shutdown");
        }
        if (read == -1) {
            // socket was been closed
            safeClose(this.inputStream);
            safeClose(this.outputStream);
            throw new SocketException("NanoHttpd Shutdown");
        }
        // 分割header数据
        while (read > 0) {
            this.rlen += read;
            // header
            this.splitbyte = findHeaderEnd(buf, this.rlen);
            // 找到header
            if (this.splitbyte > 0) {
                break;
            }
            // 8k中剩余数据
            read = this.inputStream.read(buf, this.rlen, HTTPSession.BUFSIZE - this.rlen);
        }
        // header数据不足8k,跳过header数据
        if (this.splitbyte < this.rlen) {
            this.inputStream.reset();
            this.inputStream.skip(this.splitbyte);
        }
        //
        this.parms = new HashMap<String, List<String>>();
        // 清空header列表
        if (null == this.headers) {
            this.headers = new HashMap<String, String>();
        } else {
            this.headers.clear();
        }
        // 解析 客户端请求
        // Create a BufferedReader for parsing the header.
        BufferedReader hin = new BufferedReader(new InputStreamReader(new ByteArrayInputStream(buf, 0, this.rlen)));
        // Decode the header into parms and header java properties
        Map<String, String> pre = new HashMap<String, String>();
        decodeHeader(hin, pre, this.parms, this.headers);
        //
        if (null != this.remoteIp) {
            this.headers.put("remote-addr", this.remoteIp);
            this.headers.put("http-client-ip", this.remoteIp);
        }
        Log.e(TAG, "headers: " + headers);

        this.method = Method.lookup(pre.get("method"));
        if (this.method == null) {
            throw new ResponseException(Response.Status.BAD_REQUEST, "BAD REQUEST: Syntax error. HTTP verb " + pre.get("method") + " unhandled.");
        }
        Log.e(TAG, "method: " + method);

        this.uri = pre.get("uri");
        Log.e(TAG, "uri: " + uri);

        this.cookies = new CookieHandler(this.headers);
        Log.e(TAG, "cookies: " + this.cookies.cookies);

        String connection = this.headers.get("connection");
        Log.e(TAG, "connection: " + connection);
        boolean keepAlive = "HTTP/1.1".equals(protocolVersion) && (connection == null || !connection.matches("(?i).*close.*"));
        Log.e(TAG, "keepAlive: " + keepAlive);
        // Ok, now do the serve()

        // TODO: long body_size = getBodySize();
        // TODO: long pos_before_serve = this.inputStream.totalRead()
        // (requires implementation for totalRead())
        // 构造一个response
        r = serve(HTTPSession.this);
        // TODO: this.inputStream.skip(body_size -
        // (this.inputStream.totalRead() - pos_before_serve))

        if (r == null) {
            throw new ResponseException(Response.Status.INTERNAL_ERROR, "SERVER INTERNAL ERROR: Serve() returned a null response.");
        } else {
            String acceptEncoding = this.headers.get("accept-encoding");
            this.cookies.unloadQueue(r);
            // method
            r.setRequestMethod(this.method);
            r.setGzipEncoding(useGzipWhenAccepted(r) && acceptEncoding != null && acceptEncoding.contains("gzip"));
            r.setKeepAlive(keepAlive);

            // 发送response
            r.send(this.outputStream);
        }
        if (!keepAlive || r.isCloseConnection()) {
            throw new SocketException("NanoHttpd Shutdown");
        }
    } catch (SocketException e) {
        // throw it out to close socket object (finalAccept)
        throw e;
    } catch (SocketTimeoutException ste) {
        // treat socket timeouts the same way we treat socket exceptions
        // i.e. close the stream & finalAccept object by throwing the
        // exception up the call stack.
        throw ste;
    } catch (SSLException ssle) {
        Response resp = newFixedLengthResponse(Response.Status.INTERNAL_ERROR, NanoHTTPD.MIME_PLAINTEXT, "SSL PROTOCOL FAILURE: " + ssle.getMessage());
        resp.send(this.outputStream);
        safeClose(this.outputStream);
    } catch (IOException ioe) {
        Response resp = newFixedLengthResponse(Response.Status.INTERNAL_ERROR, NanoHTTPD.MIME_PLAINTEXT, "SERVER INTERNAL ERROR: IOException: " + ioe.getMessage());
        resp.send(this.outputStream);
        safeClose(this.outputStream);
    } catch (ResponseException re) {
        Response resp = newFixedLengthResponse(re.getStatus(), NanoHTTPD.MIME_PLAINTEXT, re.getMessage());
        resp.send(this.outputStream);
        safeClose(this.outputStream);
    } finally {
        safeClose(r);
        this.tempFileManager.clear();
    }
}
  • HTTPSession.execute() 完成了 uri, method, headers, parms, files 的解析
  • 完成解析后,调用Response serve(IHTTPSession session)方法,创建了一个Response
  • 完成Response数据组织后,这里会调用ChunkedOutputStream.send(outputStream)方法将数据发出去。

到这里,主要流程结束,其他细节需大家自己去用心研读源码了。我的Demo中增加了很多中文注释,可以帮助大家省下一部分力气,就这样了

三、相关参考

NanoHttpd GitHub

NanoHttpd源码分析

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