Java Server - How to take input from InputStreamReader and convert to a String?

Question

I'm trying to get a very simple Client-Server system to work, where the Client will send a String over to the Server, and the server will then store that String into a file.

The client sends the string through:

//Other Code

sockStrm = new DataOutputStream (clientSocket.getOutputStream ());

//Other code

sockStrm.writeChars (line);

//Other code

And the Server receives the String with:

//Other code 

strm = new BufferedReader (new InputStreamReader (clientSocket.getInputStream ())); 

//Other code

stringLine = strm.readLine (); 

//Other code

When I send the string STOP, the length of the String is 4 on the client side, and on the server side the length of the String is 9 and displays as STOP

I've tried to substring the received String on the Server side, without luck.

Any pointers on how to deal with this?

laune · Accepted Answer · 2015-02-10 07:19:55Z

3

Use symmetric methods:

DataOutputStream sockStrm =...
sockStrm.writeUTF(str);

and

DataInputStream sockStrm = ...
String str = sockStrm.readUTF();

writeChars writes individual characters as two byte values. Readers follow the encoding to reconstruct the string from a sequence of bytes, which will definitely not be according to high-byte-low-byte for each character code. Hence you get some mish-mash of zero bytes with the original low-byte values so you still have a glimpse of the original string value. Using \x00 to denote a NULL byte:

S-T-O-P => on the line: \x00-S-\x00-T-\x00-O-\x00-P => prints as STOP

Use a loop over the characters of the incoming string and display their integer values (str.charAt(i)) to see the above for yourself.

edited Feb 10, 2015 at 7:19

answered Feb 10, 2015 at 7:14

laune

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