ByteArray to String and String to ByteArray error at readUTF from datainpu

Question

hi everybody this is my first post I hope I can find the help I need I have been doing some research and couldnt find the solution thanks in advanced
The Objective:
im building a client server application with java and I need to send a response from the server to the client via Socket
so the response is like this : <Signal : ByteArray> where Signal is a String so the client can Identify the Type of response
and the ByteArray is an Array of bytes containing the Information I need
The Problem:
I have an Array of bytes containing the info to send and I need to pass this byte[] to a String add some String that let me Identify the data in the client side then remove the identifier in the client side and convert the resulting String back to an array of bytes this doesnt work
The Code:
Server Side (Creating the Byte Array):
public byte[] createData(){
                ByteArrayOutputStream baos = new ByteArrayOutputStream();
                DataOutputStream dos = new DataOutputStream(baos);               
                dos.writeUTF(requestedFile.getName());
                dos.flush();
                byte[] data = baos.toByteArray();
                return data;
}Server Side (Converting the byte[] to String and Add some Identifier)
byte[] data= createData(); //Obtain the data  in a byte[]
String response = new String(data);  //Convert the Data to String
String Identifier= "14"; // to identify in the client side the data received this will be removed later
response = Identifier+response;  // add the identifier to the String
sendToClient( response.getBytes() );  //obtain bytes from the complete Response and send them to clientClient Side ( Receive the response that is a byte array containing the identifier plus the info <Identifier : info> )
            int index=response.indexOf(":")+1;  //find the index of the : so i can delete the identifier
            response=response.substring(index); // delete the identifier
            byte[] data = response.getBytes(); // obtains the bytes for the info ONLY cause the string no longer has identif
            receiveData ( data ); // send the data to be read by this method Client Side (Receive the Info sent from the server and read it)
            public void receiveData ( byte[] data ) {
               ByteArrayInputStream bais = new ByteArrayInputStream ( data );
               DataInputStream dis= new DataInputStream ( bais );
               setTotalSize ( dis.readUTF( ) ); // here is the error  it catches an EndOfFileException without read the info
            }im tried sending other values like long and int and i was able to read them but the problem is with the Strings at the ReadUTF()
Im tried to be the most clear as possible please help me this is driving me nuts
and I would really appreciatte all your comments thanks

Answer 1

lemaniak wrote:
The Objective:
im building a client server application with java and I need to send a response from the server to the client via Socket
so the response is like this : <Signal : ByteArray> where Signal is a String so the client can Identify the Type of response
and the ByteArray is an Array of bytes containing the Information I need
The Problem:
I have an Array of bytes containing the info to send and I need to pass this byte[] to a String add some String that let me Identify the data in the client side then remove the identifier in the client side and convert the resulting String back to an array of bytes this doesnt workFirst of all, well done: a nicely explained problem. I wish more people were as clear as you.
Second: I'm no expert on this stuff, so I may well be wrong, but I did note the following:
1. I can't see anywhere where you're putting out the ":" to separate your signal.
2. You seem to be doing an awful lot of conversions from Strings to bytes and vice-versa, but only your filename is specified as a UTF-8 conversion. Could you not do something like:
dos.writeUTF("14:" + requestedFile.getName());or indeed, more generically
dos.writeUTF(signal + ":" + messageBody);from inside a createMessage() method.
3. You haven't included the sendToClient() code, but your createData() looks suspiciously like what I would put in a method like that.
From what I understand, you usually want mirror-images of your streams at your sending and receiving ends, so if your client is expecting an DataInputStream wrapping a ByteArrayInputStream to be read via readUTF(), your server better be sending a ByteArrayOutputStream wrapped in a DataOutputStream created, in its entirety, by writeUTF().
But after your UTF conversion, you're adding your signal and then using String.getBytes(), which uses the default character set, not UTF.
HIH (and hope I'm right :-))
Winston