Simple DO protocol server, very similar to the HTTP protocol.

• Make some unit tests (done)
• Test on different machines (done)
• Test with different request messages (done)

• The server and clients communicate using TCP.

• All connections with the server are single-shot, that is, once server gets request and sends the response, it should close the connection.

• Server expects the request in text format (as opposed to binary format). The structure of the request is as follows:

  1. Line terminator is character 0x0a (newline character in most of UNIX systems).

  2. The first line starts with literal text 'DO' (without quotes), followed by one or more spaces (character 0x20), then a string (called parameter) consisting of characters in range [a-zA-Z0-9/_-] (upper and lower english characters, slash, underscore, and a dash). The line ends with the line terminator.

  3. Subsequent lines represents the header. Each header line starts with a header name, that consists of string of characters in range [a-zA-Z0-9-] (upper and lower english characters and a dash). The header name is followed by literal ':', and one or more spaces, and a header value, that is in the same format as the header name. Each header line is terminated by the line terminator.

  4. Header ends with an empty line, that is a line consisting solely of a line terminator.

• Server responds with literal text 'DONE' (without quotes), one or more spaces, followed by the MD5 hash of the parameter it received from the client, and a line terminator. The server may send header (in the same format as described for request). The response ends with an empty line.

git clone https://github.com/mbrandenburger/do-protocol.git
cd do-protocol
mvn package
java -jar target/do-protocol-server-1.0-SNAPSHOT-jar-with-dependencies.jar

• or use host and port parameter

  java -jar target/do-protocol-server-1.0-SNAPSHOT-jar-with-dependencies.jar --port=$port$ --host=$host$

For simple testing using netcat: http://en.wikipedia.org/wiki/Netcat

nc localhost 1337
nc -c localhost 1337 for line terminator (\r\n) testing

Some example:

[01:32 AM] do-protocol$ echo -ne "DO hallo\n\n" | nc localhost 1337
DONE 911b33ba90678bee998f75bb510757d1

[01:32 AM] do-protocol$ echo -ne "DO hallo\r\n" | nc localhost 1337
BAD Invalid protocol exception

[01:32 AM] do-protocol$ echo -ne "do hallo\n\n" | nc localhost 1337
BAD Invalid protocol exception

[01:33 AM] do-protocol$ echo -ne "DO hallo\nkey: value\n\n" | nc localhost 1337
DONE 911b33ba90678bee998f75bb510757d1

[01:36 AM] do-protocol$ echo -ne "" | nc localhost 1337

[01:36 AM] do-protocol$ echo -ne "\n" | nc localhost 1337
BAD Invalid protocol exception

[01:36 AM] do-protocol$ echo -ne "\n\n" | nc localhost 1337
BAD Invalid protocol exception

[03:59 PM] do-protocol$ cat TooLongData | nc localhost 1337
BAD TooLongFrameException

[03:59 PM] do-protocol$ echo -n X | tr X '\0000' | nc localhost 1337
[03:59 PM] do-protocol$

[05:17 PM] do-protocol$ echo -ne "DO hallo\n\n" | nc cloud2.ibr.cs.tu-bs.de 8037
DONE 911b33ba90678bee998f75bb510757d1

Stress test:

Server runs on cloud2.ibr.cs.tu-bs.de:8037. The start_clients.sh script
starts a lot of clients. After starting this script on three machines, the
server slows down but still alive =)
We can observe that simple request on a local machine needs more time to
process.

Starting some clients on three different machines:
bin/start_clients.sh

In that scenario, a request needs a little more time
echo -ne "DO hallo\n\n" | nc cloud2.ibr.cs.tu-bs.de 8037

See screen shot in bin/resources

• Netty http://static.netty.io/ Well known framework for network applications. Deals easily with different error scenarios e.g. Client timeouts, maximum amount of data. It handles all connections in a given thread pool.

• Google guava-library https://code.google.com/p/guava-libraries/ Provides several hashing functions such as MD5 or SHA-1.

• Apache Commons CLI http://commons.apache.org/cli/ Simplifies command line argument parsing.

• Simple Logging Facade for Java http://www.slf4j.org/ For flexible logging.

• JUnit http://junit.sourceforge.net/ Used for testing regular expressions and for the protocol message object.

http://www.ibr.cs.tu-bs.de/courses/ss12/vs/index.html https://netty.io/Documentation/WebHome http://static.netty.io/3.6/guide/ http://static.netty.io/3.6/api/ http://seeallhearall.blogspot.de/2012/05/netty-tutorial-part-1-introduction-to.html http://static.netty.io/3.6/api/org/jboss/netty/handler/codec/frame/DelimiterBasedFrameDecoder.html http://static.netty.io/3.6/api/org/jboss/netty/channel/ChannelFutureListener.html http://static.netty.io/3.6/api/org/jboss/netty/handler/timeout/IdleStateAwareChannelHandler.html http://static.netty.io/3.6/api/org/jboss/netty/channel/SimpleChannelHandler.html http://static.netty.io/3.6/api/org/jboss/netty/handler/timeout/IdleStateHandler.html http://static.netty.io/3.6/api/org/jboss/netty/bootstrap/ServerBootstrap.html http://docs.oracle.com/javase/6/docs/api/java/lang/Runtime.html#addShutdownHook(java.lang.Thread) http://commons.apache.org/cli/usage.html http://www.oracle.com/technetwork/java/javase/documentation/index-137868.html http://docs.oracle.com/javase/6/docs/api/java/util/Collections.html#unmodifiableMap(java.util.Map) http://www.dzone.com/tutorials/java/log4j/sample-log4j-properties-file-configuration-1.html http://www.vogella.com/articles/JavaRegularExpressions/article.html http://docs.oracle.com/javase/6/docs/api/java/util/regex/Pattern.html http://www.regexplanet.com/advanced/java/index.html https://code.google.com/p/guava-libraries/wiki/HashingExplained http://docs.guava-libraries.googlecode.com/git-history/release/javadoc/com/google/common/util/concurrent/AbstractService.html http://maven.apache.org/surefire/maven-surefire-plugin/examples/junit.html