//клиент. http://stackoverflow.com/questions/2017414/post-multipart-request-with-android-sdk большая часть отсюда
import android.content.Context;
import android.os.Environment;
import android.util.Log;
import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLConnection;
import java.util.zip.GZIPOutputStream;

public class FileMultipartSender
    {
     private Context context;
     private String boundary= "==="+ System.currentTimeMillis() +"===";
     private static final String LINE_FEED="\r\n";
     private HttpURLConnection urlConnn;
     private PrintWriter writer;

     public FileMultipartSender(Context _context)
        {
         context=_context;
         }
    private void init(String requestURL,File uploadFile,String id) throws IOException
        {
         String dir= uploadFile.getParent();
         String root="";
         if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED))
             root= Environment.getExternalStorageDirectory().getAbsolutePath();
         dir= dir.replace(root,"");
         String date= DateUtil.dateToString(DateUtil.getCurrentDate() ) +" "+ DateUtil.timeToString(DateUtil.getCurrentDate(),true);
         URL url= new URL(requestURL);
         urlConnn= (HttpURLConnection)url.openConnection();
         urlConnn.setRequestProperty(O.yps.attrs.ID,id);
         urlConnn.setRequestProperty(O.yps.attrs.DIR,dir);
         urlConnn.setRequestProperty(O.yps.attrs.DATE,date);
         urlConnn.setRequestProperty(O.yps.attrs.ENCODING,"gzip");
         urlConnn.setDoOutput(true);
         urlConnn.setDoInput(true);
         urlConnn.setRequestProperty("Content-Type","multipart/form-data; boundary="+ boundary);
         writer= new PrintWriter(new OutputStreamWriter(urlConnn.getOutputStream(),O.CHARSET),true);
         }

     private void addFilePart(String fieldName, File uploadFile) throws IOException
        {
         String fileName= uploadFile.getName();
         writer.append("--"+ boundary + LINE_FEED);
         writer.append("Content-Disposition: form-data; name=\""+ fieldName +"\"; filename=\""+ fileName +"\""+ LINE_FEED);
         writer.append("Content-Type: "+ URLConnection.guessContentTypeFromName(fileName) + LINE_FEED);
         writer.append(LINE_FEED);
         writer.flush();

         String tempPath;
         if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED) && context.getExternalCacheDir()!=null)
             tempPath= context.getExternalCacheDir().getAbsolutePath() +"/955653 Temp.gz";
         else
             tempPath= context.getCacheDir().getAbsolutePath() +"/955653 Temp.gz";
         File tempFile= new File(tempPath);
         byte buff[]= new byte[4096];
         int count;
         try
            {
             BufferedInputStream fileIn= new BufferedInputStream(new FileInputStream(uploadFile) );
             BufferedOutputStream gzipOut= new BufferedOutputStream(new GZIPOutputStream(new FileOutputStream(tempFile) ) );
             while( (count=fileIn.read(buff) )>0)
                 gzipOut.write(buff,0,count);
             gzipOut.flush();
             gzipOut.close();
             fileIn.close();

             BufferedInputStream gzipIn= new BufferedInputStream(new FileInputStream(tempFile) );
             BufferedOutputStream urlOut= new BufferedOutputStream(urlConnn.getOutputStream() );
             while( (count=gzipIn.read(buff) )>0)
                 urlOut.write(buff,0,count);
             urlOut.flush();
             gzipIn.close();
             }
         finally
            {
             tempFile.delete();
             }
         writer.append(LINE_FEED);
         }
     private String finish() throws IOException
        {
         StringBuilder sb= new StringBuilder();
         writer.append(LINE_FEED).flush();
         writer.append("--"+ boundary +"--"+ LINE_FEED);
         writer.close();
         int status= urlConnn.getResponseCode();
         if(status==200)
            {
             BufferedReader resultIn= new BufferedReader(new InputStreamReader(urlConnn.getInputStream() ) );
             String line;
             while( (line=resultIn.readLine() )!=null)
                 sb.append(line +"\n");
             resultIn.close();
             urlConnn.disconnect();
             }
         else
             throw new IOException("Server returned non-OK status: " + status);
         return sb.toString();
         }

     public String sendFile(String requestURL, File uploadFile,String id) throws IOException
        {
         try
            {
             init(requestURL,uploadFile,id);
             }
         catch(IOException initErr)
            {
             Log.d(O.TAG,"sendFile: ошибка инициализаций");
             throw initErr;
             }
         try
            {
             String fieldName="file";
             addFilePart(fieldName,uploadFile);
             }
         catch(IOException writeErr)
            {
             writeErr.printStackTrace();
             Log.d(O.TAG,"sendFile: ошибка записи файла в поток");
             throw writeErr;
             }
         String response;
         try
            {
             response= finish();
             }
         catch(IOException responseErr)
            {
             Log.d(O.TAG,"sendFile: Ошибка ответа сервера");
             throw responseErr;
             }
         return response;
         }
     }

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

//сервер. Пара мыслей отсюда http://stackoverflow.com/questions/2422468/how-to-upload-files-to-server-using-jsp-servlet?lq=1
import javax.servlet.ServletException;
import javax.servlet.annotation.MultipartConfig;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.Part;
import java.io.*;
import java.util.zip.GZIPInputStream;

@MultipartConfig
public class FileReceiver extends HttpServlet
    {
     @Override
     protected void doPost(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException
        {
         response.setCharacterEncoding(O.CHARSET);
         response.setContentType("text/plain; charset="+ O.CHARSET);
         String path;
         String id;
         String dir;
         id= request.getHeader(O.attr.ID);
         if(id==null)
             id= O.defaults.ID;
         dir= request.getHeader(O.attr.DIR);
         if(dir==null)
             dir= O.defaults.DIR;
         path= O.MAIN_DIR +"/"+ id + dir;
         File dirCheck= new File(path);
         if(!dirCheck.exists() )
             dirCheck.mkdirs();
         Part filePart= request.getPart("file");
         long fileSize= filePart.getSize();
         String fileName= filePart.getSubmittedFileName();
         String contentEncoding= request.getHeader(O.attr.ENCODING);
         BufferedInputStream fileIn= new BufferedInputStream(filePart.getInputStream() );
         path+= "/"+ fileName;
         if(contentEncoding!=null && contentEncoding.equals("gzip") )
             path+=".gz";
         BufferedOutputStream fileOut= new BufferedOutputStream(new FileOutputStream(path) );

         byte buff[]= new byte[4096];
         int count;
         while( (count=fileIn.read(buff) )>0)
             fileOut.write(buff,0,count);
         fileOut.flush();
         fileOut.close();
         fileIn.close();

         if(contentEncoding!=null && contentEncoding.equals("gzip") )
            {
             BufferedInputStream gzipIn;
             BufferedOutputStream gzipOut;
             File tempFile;
             tempFile= new File(path);
             path= dirCheck.getAbsolutePath() +"/"+ fileName;
             gzipIn= new BufferedInputStream(new GZIPInputStream(new FileInputStream(tempFile) ) );
             gzipOut= new BufferedOutputStream(new FileOutputStream(path) );
             while( (count=gzipIn.read(buff) )>=0)
                 gzipOut.write(buff,0,count);
             gzipOut.flush();
             gzipOut.close();
             gzipIn.close();
             tempFile.delete();
             }
         response.getWriter().write("Файл "+ fileName +" загружен успешно. Размер файла: "+ fileSize);
         }
     }