Errors in sending data - maybe a bug

Question

Hi, everybody. I was trying o create a program with 2 scokets, lets say socket A and socketB. The principle of this program was whatever socketA receives is beeing send through socketb and vis versa. I had creted a routine for sendind data like that:
public int SendData(String s){
try{         
     out.print(s); //this is a printwriter
out.flush();
}catch(Exception e){
System.out.println("Error in sending data"+ e.toString());
return -1;
return 0;
The strange thing was that, using a network sniffer I realised that sometimes my socket was sending characters that weren't in the string s, more precisly it was the character with hex value c2 . When I made the following modification the program worked correctly
public int SendData(String s){
try{         
     for(int i=0;i <s.length() ;i++)
          out.write((int)(s.charAt(i))); //now out is an OututSream and not a PrintWriter
}catch(Exception e){
System.out.println("Error in sending data"+ e.toString());
return -1;
return 0;
Maybe can anybody explain why was this happening? I am curious to hear your opinion!
My java -version result is:
java version "1.5.0-beta"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0-beta-b32c)
Java HotSpot(TM) Client VM (build 1.5.0-beta-b32c, mixed mode)

Answer 1

I'm not sure what you need to do. If you want to send and receive binary data, read and write bytes (or there are other ways, e.g. DataOutputStream).
If you want / need to send Unicode text, a PrintWriter / OutputStreamWriter and InputStreamReader will convert Unicode to & from e.g. utf-8. Or you can use String.getBytes() and new String(s, "utf-8") to convert:
public class t
    public static void main(String args[])
        throws Exception
        String s = "ab\u00a2\03c0";
        System.out.println("string: " + s);
        byte bytes[] = s.getBytes("utf-8");
        System.out.println("bytes: " + toString(bytes));
        String decoded = new String(bytes, "utf-8");
        System.out.println("decoded: " + decoded);
    static String toString(byte b[])
        StringBuffer buf = new StringBuffer();
        for (int n = 0; n < b.length; n++) {
            if (n != 0)
                buf.append(", ");
            buf.append(Integer.toHexString(b[n] & 0xff));
        return buf.toString();
}I'd probably use String.getBytes() instead of PrintWriter; that allows mixing text and non-text data.
Ok, quite possibly Unicode is overkill for you, and you'll be fine with the 8-bit subset. Depends on how "serious" your application is, and how likely it will need to process e.g. Cyrillic, Greek or Chinese text.
For performance, you may want buffered streams and a StringBuffer instead of string concatenation to create strings.