I am wondering if it is possible to limit/control ethernet upload and download speeds on specific transport layers (tcp/udp) using c++? I am trying to make a simple to use program that can control the speeds of any device that the ethernet is connected to. For example: Computer B is connected to computer A via Internet Connection Sharing, I use my program to limit computer B's download or upload speed to 120kbs (or any number i choose), with this I would also like to choose udp or tcp.
Basically, I want to create my own program similar to net limiter and other such software, but I also want to add my own features which many of which lack for my needs. These other features are easy enough, but I have no idea how to go about the actual limting process.
The way forward in the general case you ask about would be to create a virtual network adapter and all the monitored route traffic through it. Once that was done, then you can monitor streams between hosts or on specific ports.
Not an easy job... A starting point would be the Windows device driver kit.
If you were prepared to limit just one app, and could modify it, the task would be much simpler... wget and curl for example both offer limiting.
HTH, Ruth
Related
I'm thinking about creating EC2 instances that run industrial software. This EC2 instance should be able to receive data from Serial COM port. Is it possible to connect things like this, with eventually a serial tunneling or anything else ?
There are two parts to the answer to this question.
Yes, absolutely, this is possible in theory.
...but it might not be practical or possible for the specific purpose/application/device that you have in mind.
Terminal servers are a simple illustration of the principle. Note that in this sense, I'm not referring to a Windows Remote Desktop "terminal server," but to the generic device commonly called a terminal server which, in its simplest form, is a physical device that speaks a serial protocol such as RS-232 on one side, and TCP on the other side. RS-232 is the wire protocol of a PC "COM" port.
But a computer, configured with appropriate drivers, can have a "virtual" COM port that appears -- to software on the computer -- as an interface just like a physical COM port, but the driver for that COM port, instead of providing the software with access to literal hardware is in fact managing a TCP connection, tunneling the send and receive bits from the COM port back to the physical port on the terminal server.
The terminal server could be an actual, dedicated terminal server device, could be a full size PC, a microcontroller with network capability, a Raspberry Pi with a USB-to-Serial adapter... there are a lot of potential variations.
Problems to consider:
A lot of older industrial software seems very poorly written. This is my impression, anyway. The implementers, perhaps working at the edges of their expertise, having made certain design assumptions that work on physical COM ports but may not be compatible with such a deployment. This is less likely to be true if the systems are newer, and run on a modern OS, but back in the early days of Windows and before, this was a real mess.
License key dongles, if present, might rely on peculiarities of physical COM ports that are difficult or impossible to virtualize. The terms of the software license may constrain you from doing this.
Some equipment may be unnecessarily sensitive to the delay that is introduced by the distances involved. There are, for example, 22 ms of round-trip time in the Internet path between one of my facilities and the nearest AWS region. At 9600-8-N-1 that is the time to transmit ~23 bytes, and that's best case -- the virtualization layer and encryption will add more. The machine or the software may or may not be well-written enough to accept that kind of delay, which does not occur on a physical, local COM port.
If the machine is being controlled (not simply observed) then you need to absolutely ensure that you are not creating a safety hazard by separating the machine from its software through a virtualization layer.
"Sharing" control of a machine by software on multiple EC2 instances seems like it might be implied by your illustration, but this potentially adds an entirely different set of complexity.
In theory, yes, it's possible. I mean, even Windows remote desktop allows you to share a local COM port with the remote system, allowing remote software to access and control your local device.
In practice, this potentially requires a lot of attention to a large number of factors that vary by operating system as well as by the specific peculiarities of the devices and software in question.
EC2 connectivity is through the network interface, so I don't think a direct connection like the one you are asking is possible.
However, if you are talking about industrial devices supporting automation, chances are you can use MQTT or at least a MQTT bridge. If that's the case, you can take a look at AWS IOT Core
With AWS IOT Core you don't only get bidirectional connectivity between your devices and AWS, but also powerful analytics, device registry and management, and full integration with the AWS ecosystem.
So I have on one hand an embedded device with a camera running openCV and on the other hand a C++ (Qt) GUI. I would like to connect both i.e.:
"stream" all the output image frames/video from openCV to my remote C++ gui
send commands from my C++ gui to the embedded device
How can I do this, what possibilities do I have? I was thinking about sockets, but I don't know whether that is the easiest solution to stream the image frames from openCV to my Qt gui.
Thank you
You should give us more details about what you're trying to achieve.
You say "stream [...] to my remote C++ GUI": do you mean sending the data over a cabled connection? over a LAN network? over the Internet?
Depending on the answer this changes your system's architecture quite a bit. Especially in case you want to stream the data over the Internet. If your use case implies a LAN network, you can easily setup a peer-to-peer connection between the embedded device and the C++ app to send data. However, it's much more complicated if you want to send data over the Internet, because it is difficult to create a peer-to-peer connection if you don't have static IPs (which I'm assuming you do not have). You will need a server (which can be written with Qt as well) to work as a relay for sending data from the device to your C++ app.
Do you need actual video streaming (at 25fps), or is a low refresh rate (1-0.5fps) sufficient ?
(I'm making the assumption you want to send data over a network)
Because if a low image rate is sufficient, using WebSockets to send images on a regular basis might just do the trick.
Otherwise, you'll need to setup a UDP connection with a video buffer.
Hope this helps!
D
Quick background, I am an intern at a company assigned to a project that I have no experience with, and I need some help trying to figure out where to start.
The goal of the project is to transfer very large chunks of data from a database, to a PC and then to a Mac. I am trying to code the communication between the PC and the Mac (this has to be done in c++, I've heard Python is easier but I have to use c++). Some requirements are that the PC and Mac be directly connected via an ethernet cable, and neither computer will have access to internet. The data transfer needs to be automated, so whenever the PC detects that it has received a full dataset from the database, it transfers the data to the PC. I cannot use any third party software to do this.
So far, through the research I've done, I think I need to set up a TCP Server-Client network. I've been using the code here (http://cs.ecs.baylor.edu/~donahoo/practical/CSockets/practical/) as a guideline for socket coding. I am first trying to test this by sending files between two macs (I don't have access to a PC atm). Any guidelines as to where I go from here would be helpful. I have looked into setting up static IP addresses and such, but I get stuck from there.
I don't expect anyone to code this for me, I am just new to socket coding and this sort of project, so just looking for a nudge in the right direction. Thanks!
Before you start coding, keep in mind that to connect PC to Mac you may need a crossover cable.
Then do some reading on the wired ad-hoc networks. The last post in this discussion may help.
Finally, configure and mount shared volumes (using the stock software, no 3rd parties involved), and don't use the low-level socket interface.
Problem: Mediate USB traffic/data
I would like to accept inbound traffic on a specific USB port and replicate it exactly as outbound traffic on another specific USB port, in effect accomplishing a USB proxy. By extension, then, the connections need to be two-way. An additional requirement is that the port must be able to fake its identity (vendor ID, product ID, ...) as seen by an external device. Should the given solution also be able to dump/log the raw traffic, that would be fantastic, although not a requirement. Target platforms are Windows and/or Linux (any will do).
Before going on an epic journey and writing a custom driver, which is fairly likely to induce brain damage, I would like to ask if anyone has ever done anything similar, or could possibly conceive of the pieces needed to assemble this puzzle. :)
I don't think this is doable out of the box, without extra hardware.
What kind of device can you expect to connect to the "upstream" port of the proxy? Assuming there's a regular device (let's say a mouse, just as an example) on the "downstream" port, the device at upstream needs to be a USB host in order to handle the USB device in a meaningful way.
But you can't connect the USB port of your computer (which already is the host for all its USB root ports) directly to another computer, that's a total violation of USB's network topology. Both ports contain +5 V power rails, and if you connect those together, you're likely in for a shock. And/or a private fireworks display. Or a trip to your nearest motherboard and/or PSU retailer ...
Also, since USB is quite dynamic and so on, I don't think you can expect the bitstream from one port to be meaningful if repeated out another port, since address information etc might change.
There are 100% software USB analyzers, like http://www.usblyzer.com/, but I'm not so sure about proxies like what you describe.
At my work we have used this Beagle USB Analyzer. It sits between device and host and captures all traffic without interruption. It works in windows and linux and functions even with USB 2.0 highspeed ports.
http://www.totalphase.com/products/beagle_usb480/
Highly recommended.
So we have some server with some address port and ip. we are developing that server so we can implement on it what ever we need for help. What are standard/best practices for data transfer speed management between C++ windows client app and server (C++)?
My main point is in how to get how much data can be uploaded/downloaded from/to client via his low speed network to my relatively super fast server. (I need it for set up of his live stream Audio/Video bit rate)
My try on explaining number 3.
We do not care how fast is our server. It is always faster than needed. We care about client tyring to stream out to our server his media. he streams encoded (via ffmpeg) live video data to our server. But he has say ADSL with 500kb/s of outgoing traffic. Also he uses some ICQ or what so ever so he has less than 500 kb/s per second. And he wants to stream live video! So we need to set up our ffmpeg to encode video with respect to the bit rate user can provide. We develop server side and client side. We need a way of finding out how much user can upload per second currently (so value can change dynamically over time)
Check this CodeProject Article
it's dot-net but you can try figure out the technique from there.
I found what I wanted. "thrulay, network capacity tester" A C++ code library for Available bandwidth tracking in real time on clients. And there is "Spruce" and it is also oss. It is made using some of linux code but I use Boost library so it will be easy to rewrite.
Offtop: I want to report that there is some group of people on SO down voting on all questions on this topic - I do not know why they are so angry but they deffenetly exist.