Transmission of files through Socket or HTTP, between Android devices and desktops

I have custom socket client server data (file or text) transmission code. Now when I transfer binary files, some bytes convert onto out of range characters. So I send them in hex string. That works. But for another problem this is not the solution. This has a performance problems as well.

I took help from Java code To convert byte to Hexadecimal.

When I download images from the net, same thing happens. Some bytes change into something else. I have compared bytes by bytes. Converting into String show ? instead of the symbol. I have tried readers and byte array input stream. I have tried all the examples on the net. What is the mistake I could be doing?

My Code to save bytes to file:

void saveFile(String strFileName){  


 try{  
         URL url = new URL(strImageRoot + strFileName);  
         BufferedReader reader = new BufferedReader(new InputStreamReader(url.openStream()));  
         BufferedWriter bw = new BufferedWriter(new FileWriter(strImageDownloadPath + strFileName));  
         String line = null;  
         while ( (line = reader.readLine()) != null) {  
            bw.write(line);  
         }  
     }catch(FileNotFoundException fnfe){  
        System.out.println("FileNotFoundException occured!!!");  
     }catch(IOException ioe){  
     }catch(Exception e){  
        System.out.println("Exception occured : " + e);  
     }finally{  
        System.out.println("Image downloaded!!!");  
     }  
}   

You should take the help of this link: How to encode decode in base64 in Android.

You can send byte array obtained from a file as string by encoding into Base64. This reduces the amount of data transmitted as well.

At the receiving end just decode the string using Base64 and obtain byte array.

Then you can use @Deepak Swami's solution to save bytes in file.

I recently found out that PHP service APIs do not know about what is byte array. Any String can be byte stream at the same time, so the APIs expect Base64 string in the request parameter. Please see the posts:

String to byte array in php

Passing base64 encoded strings in URL

Hence Base64 has quite importance as also it allows you to also save byte arrays in preferences, and increases performance if you have to send file data across network using Serialization.

Happy Coding :-)