Java Networking

javaNetwork

Overview

Really two separate thoughts, but small enough they don't deserve individual posts. One is a basic HTTP Server written in Java, the sample provided will take in a word and see if it can find an image to serve for that word. The other is a basic file transfer tool, akin to FTP (Although you can't list directories or anything).

Web Server Picture

Java Byte Signing Issues

Someone e-mailed and pointed out a bug with certain files being transferred(The server was closing before the client). Turns out that Java signs byte values, so any bytes being converted with the MSB as 1 were actually subtracting from the total value, making the server expect a smaller file size. Since Java has no concept of signed vs. unsigned, you have to mask the value and convert to type with more bits. For example:

byte b = 211; // Binary is 11010011

int i = (int)(b);
System.out.println("Value: " + i);

will spit out: Value: -45
So you have to first do a mask each time you are converting a byte:

byte b = 211;

int i = (int)( b & 0xFF );

System.out.println("Value: " + i);

Now you get what you'd expect: Value: 211

Source Code

Source Tree:		http://devrand.org:8080/cgi-bin/cgit/javaNetwork/tree/
Snapshots:		http://devrand.org:8080/cgi-bin/cgit/javaNetwork/commit/
Git Access:		git clone http://devrand.org:8080/git/javaNetwork

Conclusion

Nowadays I use a Java Application Server for any webserver needs in Java. They are a little heavyweight though and there may be some applications were that's overkill. Also the network transfer tool was originally intended for a P2P program, I've since found Freenet, and believe it's better to develop on top of that instead of trying to reinvent the wheel.

Last Edited: 2010-10-16 14:38:29

+ Add a comment dd03e545bd94b3b2d7dd8fdd47b86dd02012-02-22 23:20:02.975509 UTC