在android中创建代理服务器以拦截媒体播放器的请求和响应

Question

I am trying to extract ID3 tags from live streams on an android device. Extraction of ID3 tags from live streams in not available in android by default.

The approach I want to follow is to intercept the media player request and response in a proxy server and analyze the byte data to extract ID3 tags. access to media player cache gives us a rough idea to achieve this, but I am not sure if we will be able to proxy the media player request/response. If anyone has done this or has any pointers on it, it would be very helpful ...

Thanks

Answer 1

You have to provide the MediaPlayer a localhost address and listen on the port you specify. For instance, if you have set up your proxy server to listen on port 8090, you might set the data source like:

mp.setDataSource(whateverContext, Uri.parse("http://127.0.0.1:8090"));

You will then receive requests from the MediaPlayer to which you have to respond. In order to respond properly, you simply forward the request to the remote media server (the original URI). To keep it simple you can use AndroidHttpClient to make the requests. When you get responses from the remote server, you need to write that data to the socket opened by the MediaPlayer, first the HTTP headers, followed by the entity's binary data when that is relevant.

Edit:

I haven't looked at this project very much, but it is oft mentioned as the archetypal project for using a proxy with the MediaPlayer . Their class that does the proxy work looks to be StreamProxy.java . They've used DefaultHttpClient instead of AndroidHttpClient , but it's basically the same as I described. Notice in particular their processRequest method. The following contains excerpts from that method with my comments:

// Execute the HttpRequest and receive an HttpResponse
HttpResponse realResponse = download(url);
// ...
// Retrieve the response entity as an InputStream
InputStream data = realResponse.getEntity().getContent();
// ...
try {
    // The response headers have been concatenated into httpString,
    // so write the headers to the client socket
    byte[] buffer = httpString.toString().getBytes();
    client.getOutputStream().write(buffer, 0, buffer.length);
    // Write the entity data to the client socket (repeatedly read from
    // the entity stream and write to the client socket)
    byte[] buff = new byte[1024 * 50];
    while (isRunning && (readBytes = data.read(buff, 0, buff.length)) != -1) {
        client.getOutputStream().write(buff, 0, readBytes);
    }
} // ...