Sending header info in hex format

[Mike Cunningham]

I'm supposed to send a header in hex format. I was given the following:

The header needs to be in HEX.

The "Chr" represent's a decimal value.

HEADER = Chr(85) & Chr(170) & Chr(0) & Chr(255)

If I prepend the hex value to my socket message, the hex value is FF00AA55.
Since hex is not a supported type in java, how should this be transmitted to their server using the Printwriter?

Thanks in advance.

[Stefan Wagner]

I would say hex is nowhere a type.
It's a notation-convention.
0xFF00AA55 is a 4-byte Hexvalue, and might be 4 bytes, a 4-byte Number, a 4-byte Color (transparency, RGB) or an header.
I'm not used to Printwriter - looks a bit curious to me in this context.

And the javadocs show me that I'm right:

It does not contain methods for writing raw bytes, for which a program should use unencoded byte streams.

However,

int i = Integer.parseInt ("ff00aa55", 16);

could work.

Are you bound to Printwriter, or may you use another kind of Stream?

[Stan James]

See if Integer.toHexString() does what you want. Maybe on a char by char basis.

[Warren Dew]

If you use Java Strings, be sure the other end is expecting unicode rather than ASCII.

One question - when you say "header is supposed to be in hex", do you actually mean it's supposed to be characters representing the number in hexadecimal notation, or is what's really meant that the header is supposed to be in raw binary? If the latter, you'll probably need to convert to bytes and send that.

[Stefan Wagner]

int i = Integer.parseInt ("ff00aa55", 16);
pw.print (i);

if no appropriate Stream for bytes can be used.
Of course you would allways need 4 chars to send.

What is your primary input - int, char, byte, string?

byte [] inp = {(byte)0xff, (byte) 0x00, (byte) 0xaa, (byte) 0x55};
int i = buff2Int (inp);
pw.print (i);
/** ... */
/** expects a 4-byte buf*/
int buff2Int (byte [] puf)
{
int [] buf = new int [4];
for (int i = 0; i < 4 && i < buf.length; ++i)
{
buf[i] = ((int) puf[i]) & 0x000000ff;
}
int i = ( buf[0] << 24) + (buf[1] << 16) + (buf[2] << 8) + buf[3];
return i;
}

[ August 27, 2004: Message edited by: Stefan Wagner ]
[ August 27, 2004: Message edited by: Stefan Wagner ]