Question

i am writing an application where i transfer a byte array over a socket in java.

The generation of byte array at the client end is as follows:

String vote = br.readLine();
// the data that i now encrypt using RSA

          PublicKey pubKey = readKeyFromFilepublic("alicepublic.txt");
          Cipher cvote = Cipher.getInstance("RSA");
          cvote.init(Cipher.ENCRYPT_MODE, pubKey);
          byte[] voted = cvote.doFinal(vote.getBytes());
          System.out.println(voted);
          out.println(voted.length);
          dos.write(voted,0,voted.length); // here i am sending the array to the server

on the server side i write

 String clen = in.readLine(); // read the length 
 byte[] array = new byte[Integer.parseInt(clen)]; // create the array of that length 
 dist.readFully(array); // read the array 

 // i am unable to read the array here at all !

 PrivateKey priKey = readKeyFromFileprivate("aliceprivate.txt");
 Cipher vote = Cipher.getInstance("RSA");
 vote.init(Cipher.DECRYPT_MODE, priKey);
 byte[] voteData = vote.doFinal(array);
 System.out.println(voteData);

// finally print the decrypted array

I have checked the encryption and decryption process by writing to a file it works properly.

i am using DataInput and DataOutput stream at both ends.

Can you please tell me what is wrong with my code !

Answer 1

Don’t mix reading character data and binary data on the same stream (at least, not with different streams). you didn’t show the type of “in”, but i’m guessing it is a BufferedReader (the key point here being “buffered”). BufferedReader will read more than the next line, so part of your byte[] is sitting in your BufferedReader. use the same DataOutputStream/DataInputStream for all operations on the stream. if you need to write textual data, use writeUTF/readUTF. when you write the length of the byte[], just use writeInt/readInt.