Book Image

Groovy 2 Cookbook

Book Image

Groovy 2 Cookbook

Overview of this book

Get up to speed with Groovy, a language for the Java Virtual Machine (JVM) that integrates features of both object-oriented and functional programming. This book will show you the powerful features of Groovy 2 applied to real-world scenarios and how the dynamic nature of the language makes it very simple to tackle problems that would otherwise require hours or days of research and implementation. Groovy 2 Cookbook contains a vast number of recipes covering many facets of today's programming landscape. From language-specific topics such as closures and metaprogramming, to more advanced applications of Groovy flexibility such as DSL and testing techniques, this book gives you quick solutions to everyday problems. The recipes in this book start from the basics of installing Groovy and running your first scripts and continue with progressively more advanced examples that will help you to take advantage of the language's amazing features. Packed with hundreds of tried-and-true Groovy recipes, Groovy 2 Cookbook includes code segments covering many specialized APIs to work with files and collections, manipulate XML, work with REST services and JSON, create asynchronous tasks, and more. But Groovy does more than just ease traditional Java development: it brings modern programming features to the Java platform like closures, duck-typing, and metaprogramming. In this new book, you'll find code examples that you can use in your projects right away along with a discussion about how and why the solution works. Focusing on what's useful and tricky, Groovy 2 Cookbook offers a wealth of useful code for all Java and Groovy programmers, not just advanced practitioners.
Table of Contents (17 chapters)
Groovy 2 Cookbook
Credits
About the Authors
About the Reviewers
www.PacktPub.com
Preface
Index

Using Groovy to start a server on the command line


In this recipe, we continue to explore the groovy command's features at one's disposal. This time, we show how to create a process capable of serving client requests through TCP/IP directly from the command line and with one line of code.

How to do it...

The command-line option that we are going to use for this purpose is -l:

  1. By using the -l option, it is trivial to start a simple socket server in Groovy:

    groovy -l 4444 -e "println new Date()"
    
  2. The previous line will start a server that listens to port 4444 and returns the date and time string for every line of data it receives from the clients:

    groovy is listening on port 4444
    
  3. In order to test whether the server actually works, you can start any telnet-like program (for example, KiTTY, if you are on Windows) to connect to a localhost on port 4444, and type any string (for example, What time is it?), and press Enter. The server should reply with a date/time string back as shown in the following screenshot:

In this way, you can quite easily organize communication channels for ad hoc notifications on different hosts.

See also

  • Executing Groovy code from the command line

  • Using Groovy as a command-line text file editor