Java Chat program

BrokenArrows

Im in the process of making a very simple chat program for a college project.
Two pc's connect to a server program and a chat can commence.

Its a simple program but works.

However i want to improve the program for my own uses.

I want each chat client to be able to detect when a server is available.

How would this be implemented.

The program is for use on a LAN network so would it be possible to send a broadcast message and the ones that are running the client would detect the message.

damnyanks

Do something to do a hand shake with the server be it a "Are you alive" message (Ping etc.)

If it is... then it's alive
if its not... then its not live

elvis2002

you could send a message to the multicast IP address instead of the server IP. If the program detects a message as 'Are u alive? say', it sends back "Im Alive, my IP is...."?

aidan_walsh

elvis2002 wrote:

you could send a message to the multicast IP address instead of the server IP. If the program detects a message as 'Are u alive? say', it sends back "Im Alive, my IP is...."?

You could, but there are relatively few multicast enabled routers out there...

dingding

Both would have to be on the same segment of the network. Routers intentionally block broadcasts, they only allow certain ones through i.e. dhcp requests and even this functionally has to be enabled on the router.

jellie

if you want to change it for personal use wont you have to consider security, firewalls, etc?

dunno how important these would be to you

BrokenArrows

damnyanks wrote:

Do something to do a hand shake with the server be it a "Are you alive" message (Ping etc.)

If it is... then it's alive
if its not... then its not live

That would be easy enough to do once the IP address was always the same.

I was thinking more along the line of anyone could start up a server and the client would be able to detect the server.

You know the way in multiplayer games eg COD when you start up a LAN game and all the other people that want to play can just refresh a list and all the available LAN server show up on a list.

How is that implemented?

aidan_walsh

That would usually be because for internet games the game is connecting to a central registry where all active games are listed, and the status of the game would be sent periodically to the server. For LAN games, LANs would usually have a very limitied IP range, so it would be more feasible to send out a "whose serving" packet to all addresses on the LAN and see who replies.

BrokenArrows

aidan_walsh wrote:

...For LAN games, LANs would usually have a very limitied IP range, so it would be more feasible to send out a "whose serving" packet to all addresses on the LAN and see who replies.

I wish to implement the chat on a LAN so could i do the same and how?

djmarkus

i developed this exact thing in VB, of course it'd be alot more difficult in java. i used UDP broadcast to broadcast a "Im Here" packet.

BrokenArrows

Why do you say it would be more difficult in java

aidan_walsh

BrokenArrows wrote:

I wish to implement the chat on a LAN so could i do the same and how?

Questions to ask yourself:

What IP address is my program on?
What can this tell me about the range of IPs my LAN is on?
How can I check another IP address for a server?

BrokenArrows wrote:

Why do you say it would be more difficult in java

Probably because he is talking out his arse.

zoro

aidan_walsh wrote:

Probably because he is talking out his arse.

Completely ...

To the OP: This project is certainly possible, but your first step should be to get a simple echoserver up and running.
This will allow you to connect to your server from 2 clients, and they should be able to talk to each other.

Once it's working, make the server multi-threaded and then start to work on your protocol.
ie: MSG Zoro Hey there everyone
would mean that the user "Zoro" is saying "Hey there everyone" to the entire chat-channel.

It's not a very complicated project, so don't worry yourself too much about it.
Reread my reply, the start to your project can be found on google if you look for it (it's where I got the base for my chat application after all) - all you need to do it make it work as you want it to.

Zoro

djmarkus

aidan_walsh wrote:

Questions to ask yourself:

What IP address is my program on?
What can this tell me about the range of IPs my LAN is on?
How can I check another IP address for a server?


Probably because he is talking out his arse.

Eh, no, VB is piss easy, easily the easiest language i know(probably not the most efficient), thats out of c, c++, VB and java, unless you know both vb and java dont question me.

aidan_walsh

djmarkus wrote:

unless you know both vb and java dont question me.

I do, so I will. Thanks anyway.