Instant Messengers are very popular on PCs, with the advancement of mobile technology it has become possible to connect to MSN, Yahoo!, ICQ and other instant messenger services through mobile phones. The possibility of using internet from mobile devices and the possibility of executing J2ME Java programs on mobiles makes signing on to instant messenger services using mobile devices. The only major problem becomes the input of messages as only a few can type in messages very fast. Particularly with the low cost of mobile internet and reducing cellular phone prices, it is only a matter of time before every cell phone user would also be connected to an instant messenger services. It is assumed the reader knows how to transfer programs to his mobile phone and has subscribed to mobile internet service.
Most of the new mobile phones come with a built in chat client based on the wireless village technology, it is known as "My Friends" on SonyEricsson phones. Although it certainly is not going to be used a lot in future because it is based on a polling system it is currently the best option for most phones. The phone has to connect to the server every few minutes and get the new status of online contacts or get new messages. Therefore the messages are not 'Instant', there is some delay between the messages.
Although this technology has been around for sometime not many people seem to know about it. Mostly because the phone manufacturers or the cellular service providers do not provide a server which could be used with the client built in on the phones. However there is a Wireless Village service which provides this service for free. Check www.yamigo.com for using this.
The one very big advantage of using this over the other methods is that phones have an option to use this in the background. This means u can play a game and use this simultaneously. The very big disadvantage is that you have to add every person whose online status you wish to be notified of in your Yamigo contact list as well.
This is probably the best Instant Messenger Client available for mobile devices but one drawback is that it would only run on Symbian phones. Most of the phones have only Java capability and cannot use this. This client comes with a well designed user interface and can connect to MSN, Yahoo!, ICQ and AIM. This is the second most common option after web or WAP based clients. It is to be noted that Symbian OS allows multiple programs to be run at once. I have not check this technique but have seem others use it very successfully.
Although the Agile Messenger website says they have got a Java version of the program, it is not available for download freely and you presumably have to ask your cellular service provider for this J2ME version.
Jabber technology has been around for sometime, this lets users to connect to multiple instant messenger networks simultaneously. This consists of a server and client. The server stores the usernames and passwords for all networks. You have to login to the server using a jabber client. There are now several Jabber clients available for mobile phones. A very good service especially for mobile phones is available at www.jabber.nu.
They have got several builds of their client for different mobiles. However the older phones which have MIDP1.0 would not be able to use most of the jabber clients as they do not have TCP socket support.
This is the most popular method as all it requires is a phone that support mobile internet. No Java support, Symbian OS or anything else is required. All this needs is a WAP browser. The service is available on www.e-messenger.com. However in the mobile you have to enter: mob.e-messenger.net. I have successfully used this on many phones. There are major drawbacks as the login screen would not remember your sign in name. If you have to use something else on your mobile you would have to close the WAP browser. This site is only for MSN, there might be other such sites for other networks.
There are also other methods available, most of which are commercial and you have to pay to use those services, but I don't think that it is worth paying them as you can not get the chatting experience on PC. All the methods I have listed above can be used for free although you have to pay for your internet subscribtion.
It would not take long before a client and server is created so that anyone can run the server on his 24/7 static IP internet connection to which the client would connect. So that users can avoid giving their login information to third parties. Such a client/server application would be made so that the data transfer between the mobile and the server is reduced and mobile internet charges are lower.