Virtual channels for VNC? - add-in

Does anybody know weather VNC (RFB) supports virtual channels and add-ins to them like it is in the RDP (Microsoft Terminal Services)? I just want to transfer my own data across a VNC connection...

VNC/RFB does not have virtual channels unfortunately.
Here is the best reference I've found to the RFB protocol: http://tigervnc.org/cgi-bin/rfbproto
Without knowing more about what you are trying to send and which direction(s), there are a few of options that come to mind:
The tight encoding has file-transfer support. There is a poorly formatted specification for the full tight encoding here: http://vnc-tight.svn.sourceforge.net/viewvc/vnc-tight/trunk/doc/rfbtight.odt?revision=3619
If you have control of both client and server, then you could define a custom encoding that allows you to send your data. The client would advertise that it supports the encoding and if the server supports it then it will start using it.
You could use the clipboard messages (ClientCutText and ServerCutText) and if you need to send binary data that create a custom encoding the data as ISO 8859-1 (Latin-1). The downside is that if the server doesn't support it and the client sends the data it will get pasted to the server.
If you just need to send from the server to the client, then you could use a framebufferUpdate message that sends data outside the current viewport (i.e. 123 pixels beyond the right side of the viewport). Clients without support may not handle this well though.
Another option if you just need to send from the server to the client, is that you could send a framebufferUpdate within the viewport with a special marker and then immediately send a framebufferUpdate (even in the same packet) with the real visible data to replace it. This would work with existing clients (a bit more overhead). Clients might see brief flicker though.

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TCP Listener in Delphi

I want to implement a demo application to listen data via TCP/IP.
Data Transmitter will transmit a series or ASCII char or a series of string all the time. It feeds data into TCP/IP address (eg. 127.0.0.1:22) This could be a GPS transmitter.
I want to implement a demo application for receiving data by clicking the start button and listening to the data via TCP/IP and display it accordingly.
Correct me if I am wrong, I don't think I can use Server/Client server for this purpose. I tried to create a client application with TIdTcpClient, it receives only one time data. I don't think Indy has a TCP listening component.
Thanks in advance.
If you wanna monitor network comunications between some device and some other program on your computer using of TIdTCPServer won't work. Why? Once Indy will read network data it will mark it as processed and delete it from network buffer. So that data probably won't even reach to the other program on your computer. Workaround for this is that you design your application to actually work similar as network bridge. Your application listens to the data on one port and then forwards that data on another port on which the other program is listening. But the main problem is that you have to make this to work both ways.
What you need is somekind of a component which is able to peek at the network data but don't interact with it. This is usually done on driver level.
Now if it is not abolutely necessary to have such functionality in your own software but you are only interested in getting the data I recomend you try Wireshark (http://www.wireshark.org/). Wireshark is a verry powerfull freware software which alows you to monitor all netwrok traffic on basically all protocols without causing any interuptions. In order for this software to work it instals special driver which serves for intercepting the network data.
Maybe you would want to use same driver in your application if this functionality needs to be in your application.
Based on your diagram I think that your implementation could also be based on a message-oriented middleware, using a message broker which receives the GPS transmitter or other data.
The message broker would then store the data internally and forward it to all interested clients which are connected. A typical messaging pattern in this case is a "Topic", which broadcasts the messages similar to a radio station.
So the middleware will ensure that the information will be collected (optionally also persisted to disk) and then guarantees the delivery to the receivers. This can be done even in a way where receivers which have been off-line for a while still receive the GPS messages created while they where not listening ('retroactive consumers').
There are many popular free open source message brokers, and most of them also can be used with Delphi.

Send text messages between two computers through internet with delphi?

I want to write a app which will run on different computers and need all of then to communicate with each other like "utorrent" (peer to peer). This app only will send text messages.
How can I do this? I mean sending one message to remote computer on the internet?
I have a website and every app at start can send some information to it and find information of other apps on other computers (with PHP) but I do not know how address one computer through internet and send the data directly to that. I can find the ip address with PHP but it is the ip address of router (ISP).
How a message reaches a computer? I'm wondering about addressing every computer?
My brain really stuck here, I really appreciate any help. Thanks.
In a peer-to-peer network there's no centralized server for transmitting the data from one client to another, in this case the clients must be able to act as both the server and client. This means that either you'll have to be using UPnP like most modern torrent clients, which handles port forwarding in the router, or you'll have to manually forward a port to the computer in the router.
A centralized server (like a torrent tracker) is usually used to make the clients aware of each other's existence and tell them where to connect. This is where your PHP script comes in, though PHP might not offer the most effective way of doing this, assuming you're using it in combination with a webserver to serve the data though the http protocol.
As for actual text communication, you could use the Indy socket library for that. I found this example, basically which shows how to do it: http://www.ciuly.com/delphi/indy/indy-10-client-server-basic-demo/

Sending large amounts of data from windows app to service app

I'm building a system with some remote desktop capabilities. The client is considered every computer which is sharing its desktop, the server is considered a central server with a database which receives the images of all the multiple desktops. On the client side, I would like to build two projects: A windows service application and a VCL forms application. Each client app would presumably be running under a different user account on the computer, so there might be multiple client apps running at once, and they all send their image into this client service, which relays them to the central server.
The service will be responsible for connecting to the server, sending the image, and receiving mouse/keyboard events. The application, which is running in the background, will connect to this service some how and transmit the screenshots into the service. The goal is that one service is running while multiple "clients" are able to connect to it and send their desktop image. This service will be connected to the "central server" which receives all these different screenshots from different "clients". The images will then be either saved and logged or re-directed to any "dashboard" which might be viewing that "client".
The question is through what method should I use to connect the client applications to the client service to send images? They will be running on the same computer. I will need both the abilities to send simple command packets as well as stream a chunk of an image. I was about to use the Indy components (TIdTCPServer etc.) but I'm sure there must be an easier and cleaner way to do it. I'm using the Indy components elsewhere in the projects too.
Here's a diagram of the overall system I'm aiming for - I'm just worried about the parts on the far right and far left - where the apps connect to the service within the same computer. As you can see, since there are many layers, I need to make sure whatever method(s) I use are powerful enough to accommodate for streaming massive amounts of image data.
Communicates among processes, you can use Pipe/Mailslots/Socket, I also think while sending a stream file Shared Memory maybe the most efficient way
I've done this a few times now, in a number of different configurations. The key to making it easy for me was using the RemObjects SDK which took care of the communications part. With a thread that controls its state, I can have a connection to a server or service that is reliable, and can transfer anything from a status byte through to transferring many megabytes of data (it is recommended that you use small chunks for large data so that you have more fine grained control over errors and flow). I now have a set of high reliability templates that I can deploy to make a new variation quite easily, and it can be updated with new function calls without much hassle (first thing I do is negotiate versions between the client and server so they know what they can support). Because it all works at a high level, my code is just making "function calls" and never worrying about what the format on the wire is. Likewise I can switch from their binary format to standard SOAP or other without changing the core logic. Finally, the connections can be local, to the same machine (I use this for end user apps talking to a background service) or to a machine on the LAN or internet. All in the same code.

Secure communication across a LAN

I want to make a small app that collects data from a device attached to a serial port and passes it across a LAN to another app which stores it in a database.
I have done this already in one app on a single PC, so will effectively be splitting the app in half.
I have zer0 experience of network programming.
I want something "secure" meaning that the data are in some way encrypted and relatively straightforward to implement.
At the moment communication is one way, but I might want so send control data in the return direction later.
Can someone please recommend a protocol (preferably one which is commonly used for this sort of thing) and post a small code snippet of how to send and receive - let's say a data structure with a string for user name and an integer for age.
Or, just point me at a URL.
Thanks in advance.
Answer: I'm going with IpSec and Exchanging Data over the Network using Delphi
You can simply use IPSec between the two computer and the operating system will encrypt the channel without any need of changing the applications.
Other option may be DCOM (if you use the Enterprise version of Delphi Datasnap supports it) that can also encrypt the communication (must be set in the configuration, works best in a domain).
Both options don't need certificates or the like, and the OS will take care of storing the keys safely.

Need to communicate with a box using Modbus over TCP/IP from my cloud-based server

So I don't have much experience with Modbus but my problem is essentially what's in the title. Would I need a controller that talks to the box and then reformat the message and pushes it to the server? Or can the server talk to the box directly? BTW, my cloud app uses Rails if that helps. I'm not sure what other information is required so feel free to let me know.
Thanks.
All you need is a MODBUS library for Ruby.
Modbus originated as a serial master/slave protocol with two different modes; 'ASCII' and 'RTU'. The different modes have different packet formats (one uses ASCII characters, and the other uses binary), different rules for detecting the start and end of packets, and different error detection (checksum or CRC). Modbus over TCP/IP basically takes the 'RTU' packet, discards the CRC, adds some extra addressing, and wraps it up in a TCP packet. Provided you are happy to implement the code to construct (and interpret) packets in your cloud app then there's no reason why the server cannot talk to the box directly.
One thing you should bear in mind is that a 'Modbus client' issues commands to a 'Modbus server', which then responds. So you need to work out whether your box is a 'Modbus client' or 'Modbus server'.
The only thing I'm not sure about is IP addresses. If your cloud-based server gets a different IP address each time it runs then that might be a problem if it is acting as the 'Modbus server', or if your box has an access control mechanism.
All the documentation can be downloaded from www.modbus.org

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