Tcl (Tool Command Language) is a very powerful and easy to learn dynamic programming language, suitable for a very wide range of uses. Tcl is regarded as one of the best-kept secrets in the software industry. This book gives you a hands-on experience on Tcl, helping you develop network-aware applications using this mature yet evolving language.

This book shows you how to create network-aware applications with Tcl language. Packed with practical examples, the book not only takes you through the implementation of network protocols in Tcl, but also key aspects of Tcl programming.

The book starts with the basic element of Tcl programming as we take a look at the syntax and fundamental commands of the language. To get us ready for network programming, we look at important Tcl features such as object-oriented programming, accessing files, packaging in TCL, event driven programming, and multithreaded applications. To create standalone single-file executable applications with Tcl we take a look at the Starpack technology, and ensure that we'll be able to create robust applications with a thorough coverage of troubleshooting and debugging Tcl applications.

The book is really about network programming, and it will not let you down with its deep coverage of these topics. Of course we look at protocols, but there are plenty of practical examples to keep things moving along. We start with the TCP and UDP protocols, and look at some other protocols to see examples of synchronizing time with other servers, querying user information and authenticating users over LDAP and performing DNS queries.

The book explains Simple Network Management Protocol (SNMP), which is often used for monitoring and gathering information from various devices, such as routers, gateways, printers and many other types of equipment. We'll also look at web programming in Tcl; processing the requests coming from the clients via the HTTP protocol and responding to these requests. You'll be able to create a complete solution for creating a client-server application in Tcl.

To round things off, you'll see how to secure your networked applications, build public key infrastructure into your application and use Tcl's safe interpreter feature to reduce risk of running code from unknown source.

This book will be help you discover a range of network protocols and concepts and show how to implement them in Tcl

What you will learn from this book

• Get to know the the tools available to ease up development of Tcl code
• Discover Tcl's approach of using events over threads, which is very different from many other languages
• Learn the VFS feature that allows the usage of Metakit database as normal file system
• Create loggers, define log levels, write your logs to file or channel, and trace the execution of your code
• Get to know the key differences between free TclPro Debugger and paid ActiveState Tcl Dev Kit Debugger
• Handle different text encoding, dependent on the region you live, and create multi-language, internationalized application with msgcat package
• Handle UDP communication in Tcl was presented, with TclUDP extension as the implementation
• Manage files remotely over File Transfer Protocol (FTP) and learn to download a file from a web site using Hypertext Transfer Protocol (HTTP).
• Learn the usage Lightweight Directory Access Protocol (LDAP) to look up information and/or authenticate users, manually querying host names and time servers
• Get to know the Tcl package Scotty that handles SNMP and provides a Tk based GUI application that can be used for inspecting devices, discovering systems within our network and browsing data that can be retrieved over SNMP
• Use Tcl code as legacy CGI scripts and improve it with ncgi package
• Create client-server application based on HTTP protocol and Tclhttpd as embedded web server packed into Starkit technology for easy deployment
• Connect to XML-RPC services and issue methods remotely, and easily integrate with major blogging engines
• Create SOAP services using Tclhttpd and Web Services for Tcl; define complex data types for storing structured information
• Learn to use encrypted connections from Tcl and the method to make sure you know whom your application is communicating with

Approach

The book is written so that both experienced and novice Tclers can find useful information inside. It starts with quick introduction to Tcl and its networking support for those who are less familiar with them.

Authors focus on showing practical, yet simple examples for each module and command described so that reader understands how to use them when solving the real life problems. The examples given are useful programs that try to solve real-world needs. All sample programs are clear and concise yet nothing essential is left out and the programming style focuses on readability rather than on stylistic rigor or efficiency.

Who this book is written for

This book is for Tcl developers with basic network programming concepts, who want to add networking capabilities to their applications. Working knowledge of Tcl and basic experience of network protocols will be useful. The reader should be familiar with basic concepts used in modern networking - keywords like TCP, HTTP or XML should not be a mystery. The book does not require advanced knowledge of Tcl - the first chapters will swiftly introduce the reader into it, allowing refreshing the information or gaining a quick overview of the Tcl language abilities.