How can I transload data between two delphi applications over internet?

Hi let me make my question clear. Two people using my app are connected to the internet. Both have each other's IP and they want to chat (like Y!messanger) with each other. I think I need to use Indy components; r开发者_JS百科ight? Which component should I use? Thanks in advance

Have you looked at any of the demos on Indy's website yet?

In general, you are looking to create a "Client/Server" type application. A quick Google search for "indy client server example" pulls up lots of results, including this one: http://www.devarticles.com/c/a/Delphi-Kylix/A-Real-World-Client-Server-Application-in-Delphi/

In reality, this gets a lot more complicated when you have firewalls and NATs with private IP addresses. You will have to consider how your application will either get around or through these types of technologies.

Similar to what Scott said, I think that your biggest problem is getting them talking to each other. My computers at home go through a router, which blocks all incoming connection requests (i.e. requests to start a conversation between two computers) from the Internet. My computers can send connection requests OUT, and start a conversation that way, but unless you modify the router (port forwarding) my computers can not receive connection requests.

You need a server somewhere to which both people will connect, that can then relay messages back and forth. To get really tricky, once the connection is made to the server the two computers can then be put into direct contact, but that involves UDP packets and some clever magic.

You don't have to use Indy components, you just need anything that will handle communications over the network. Any HTTP or sockets network stack will do. Indy is the defacto standard for Delphi Win32.

To do network communications, you will need to create a listener object or service on machine A and a sender object on machine B to send a network message from A to B. To send a message from B to A, you will need a reverse path as well - 4 objects total to perform bidirectional comms. Some object wrappers hide this detail internally. I don't recall offhand whether Indy hides this or not.

It would probably be easiest if you use a common TCP/IP protocol for your machine to machine communications, such as HTTP. This will make it easier to get your connections through firewalls and proxies that frequently exist between arbitrary users. To avoid conflicting with any HTTP web services that might be running on either machine, you should use a custom port number with the IP address: 192.168.1.10:12345, not the standard HTTP web server port 80. This is what most of the IM clients do.