Encoding File Over Socket

Question

I have been spending forever on this and can not seem to work it out. I am self taught and not very familiar with this so forgive me if it is a remedial question. I am sending data from Android to .Net server. Data is getting corrupt on encoding, I know this I am just not sure how to fix. I am using the .Net Async server sample code found here: Microsoft Async Sample

My Android client code is:

try {
            final Socket sock = new Socket();
            final int timeOut = (int) TimeUnit.SECONDS.toMillis(5); // 5 sec wait period
            sock.connect(new InetSocketAddress("localhost", 11000), timeOut);

            if (sock.isConnected()==true){
                BufferedReader in = new BufferedReader(new InputStreamReader(sock.getInputStream()));
                BufferedWriter out = new BufferedWriter(new OutputStreamWriter(sock.getOutputStream()));

                String FileName = "myfile.jpg";

                StringBuilder hd = new StringBuilder();
                try {
                    String FilePath= Environment.getExternalStorageDirectory() + "/mydir/" + FileName;
                    File file = new File(FilePath);
                    FileInputStream is = new FileInputStream(file);
                    byte[] chunk = new byte[40960];
                    int chunkLen = 0;
                    while ((chunkLen = is.read(chunk)) != -1) {
                        //String str = new String(Base64.encodeToString(chunk, Base64.NO_WRAP));
                        //String str = new String(chunk, "ASCII");
                        String str = new String(chunk, "UTF-8");
                        out.write(str);
                    }
                    //out.write(hd.toString());
                } catch (FileNotFoundException fnfE) {
                    // file not found, handle case
                } catch (IOException ioE) {
                    // problem reading, handle case
                }

                out.write("<EOF>");
                out.flush();

                StringBuilder returnString = new StringBuilder();
                String line;
                while ((line = in.readLine()) != null) {
                    returnString.append(line).append('\n');
                }

                out.close();
                in.close();
                sock.close();
            }else{
                sock.close();
            }

        } catch (IOException e) {
            e.printStackTrace();
        }

As you can see in my comments, I have tried base64 and UTF-8. I get all kinds of errors on the server when I do that. If I use Base64 I get not part of Base64 error (extra padding etc.). UTF8 writes the file but it is corrupt. When I send it all as one Base64 string it works fine as I use 'Dim data As Byte() = Convert.FromBase64String(FileData)' but as expected it throws memory errors in Android for large files hence the chunking. I am sending some plain ASCII text along with it so I parse out the non-ASCII stuff to write the file. I am super stuck, any help would be much appreciated. Thanks in advance.

score 0 · Answer 1 · answered Oct 28 '17 at 00:01

0

You don't have to encode it at all. Just write it directly as bytes using an OutputStream. Simpler, quicker, better.

answered Oct 28 '17 at 00:01

user207421

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I know you are correct but the server looks for and I also needed to send some other data with the file. I used tags like the so it was just the way I did it. Again, new to this domain so it may end up I change it. Thanks for this though. – nathan Oct 28 '17 at 00:09
The server should not look for ``. What if it occurs in the file? See my answer in the duplicate for the correct way to do his. – user207421 Oct 28 '17 at 00:17

score -1 · Answer 2 · answered Oct 27 '17 at 23:50

I found the answer. It was so weird but makes sense now.

 byte[] chunk = new byte[30000];
                int chunkLen = 0;
                while ((chunkLen = is.read(chunk)) != -1) {
                    String str = new String(Base64.encodeToString(chunk, Base64.NO_WRAP));
                    out.write(str);
                }

I had to change the chunk size to a multiple of 3 then my base64 encoding worked great. Found it here and gave an up vote. Thank you 'mjv'. Link to the answer

For this to even begin to work it would require the serve to implement an undisclosed base-64 decoding step. — user207421, Oct 28 '17 at 07:57

Encoding File Over Socket

2 Answers2