Instant messengers are programs that you let chat in real time with other Web users. Example of instant messengers include those produced by MSN, AOL and Yahoo. Making your own messenger program involves applying the networking and other functions of a high-level computer language, such as Java. The benefits of making your own messenger application include the ability to add features not found in off-the-shelf messengers. For example, you could provide a function to retrieve Web content besides chat text, such as messages from your email account.
Run several messenger programs whose source is freely available. (These are called "open source" programs.) Examples of open source messengers include Pandion, Valhalla Chat and PlanetAMessenger.
Write -- for the messenger that you feel is ideal -- detailed notes describing what features of the program you'd like to customize. For example, you may write "The emoticon buttons are cool, but should be on the main screen, not buried under a menu."
Click the link to download the messenger program's source code and documentation describing how to compile the program. This link will be on the same site as the one with the link to the executable program.
Read thoroughly the downloaded documentation, taking special note of the language the program was developed with (such as Java or C).
Install a platform for compiling and debugging programs in the language you took note of in the previous step. Oracle provides a Java development platform on their Java subdomain. Open Watcom, among others, makes a free platform for developing applications in C.
Load the messenger program's source files, one by one, into a text editor like Notepad. Print each file from the text editor.
Type, into a new set of source files made with your text editor, the messenger program's source code. This task makes you read step 6's printed source with an intense concentration that will begin revealing how the program works.
Read your development platform's documentation for compiling programs, then compile the source type typed in the previous step. If the messenger doesn't work as you expected, trace through or debug the program, as directed by your development platform's docs.
Select, in Windows Explorer, the messenger source files and press "Delete."
Retype each source file as you did in step 7. In this typing session, use your memory as the primary resource, not the printed source code. Use the printouts only when you forget a statement. Repeat this step until you can type the messenger program from memory. Typing from memory rather than a printout will complete your understanding of the messenger program, which you began to build in step 7. This understanding provides enough skill to modify and personalize the messenger.
Edit, with your text editor, existing source code and write new source as needed to effect the program changes you described in step 2. Recompile and debug the program to produce your completed instant messenger.