I am writing a chat application in QML/C++. I have already implemented an option to chat locally (with people in the same network) and I am currently working in implementing a bluetooth chat option.
However, one early user of my application suggested me to implement an ad-hoc based chat option that would communicate each device directly (without the need of a router, in other words, peer-to-peer). This feature would be very useful if the user(s) are located in a place without an internet access point, say a music festival or in an event.
My application uses the Qt framework and it has the necessary tools for me to implement this feature, however, I am a hobbyist programmer and I don't have a lot experience dealing with network connections.
Do you know any way to implement this ad-hoc, peer-to-peer feature? (or know any helpful websites/links).
Thanks in advance,
Alex.
You can use TCP or UDP protocol for your chat application.
TCP = connected protocol
UDP = "broadcast" protocol, more speed
Example here :
http://qt-project.org/doc/qt-5.0/qtnetwork/network-chat.html
Or here : http://qt-project.org/doc/qt-5.0/qtnetwork/examples-network.html
Yekmen
Related
I am wondering what is suitable for my case, using espeasy or Tasmota. I know espeasy is using http requests and Tasmota is using mqtt.
I want to control my sonoff devices by a raspberry pi that is acting as a home automation hub, and it in turn send updates and receives commands from AWSIoT platform. For interacting with AWSIoT platform, it uses mqtt.
What are the pros and cons of using either? and will it cause problems if I control several sonoff devices with http, while using mqtt for AWSIoT? or better use mqtt for all AWSIoT and sonoff?
I am not an expert on the topic but have tried a few things and got some insight for you on why to prefer MQTT over HTTP.
Security. Remember that the 'S' in IOT stands for security. Joking aside. I have not seen an option for encryption (HTTPS) of the HTTP-traffic for tasmota. (May the internet correct me if I am wrong) So choosing HTTP means your user/password (which are not a requirement but should totally be used) are transfered via URL query parameters as plain text. MQTT has built-in mechanisms for encrypting the traffic. I haven't been able to get that working in my network but I'm trying.
Flexibility/Reliability. With MQTT/Tasmota you have the ability to implement automations that do not rely on your home automation hub by having your devices publish MQTT-messages directly to each other for interaction. For example if you would like to implement an emergency off button that turns multiple devices off you do not want that to rely on your home automation server. Doing this with HTTP 'could' be done too but requires all users/passwords of all the devices to reside not only in your home automation hub but also on other single devices.
Networking. Adding new devices to your hub should be as easy as possible. In matters of HTTP your home automation hub has to know how to find your devices via IP-addresses or domain names since it has to resolve a URL. When using MQTT you just connect your tasmota devices to your broker and use their topic in the home automation hub. The devices do not even need to have a static IP or reachable domain name of mDNS name of any sort. That's in an essence what makes pub/sub for IOT so interesting in the first place.
Existing support. Before building your own home automation solution be sure to check out home assistant (my favorite) or any of the other home automation solutions if they fit your need. Do not reinvent the wheel. A tipp for home assistant: Do not use MQTT auto discovery in combination with tasmota. This is the only thing that has not worked out for me. Manually registering devices works reliably.
Hope that helps. If you still prefer HTTP checkout the app "Tasmota control".
I've been asked to implement VPN capabilities in an existing software project on an embedded system, in order to make the device available via network to an external server while avoiding trouble with firewalls (no need for encryption, just to make it accessible).
Unfortunately, the embedded system is based on a Cortex-M4 MCU, therefore Linux, which would allow for VPN nearly out of the box, is not an option. All I've got is an RTOS and a working LwIP stack.
I've used VPNs in the past. However, my network knowledge is rather limited concerning implementing VPNs, so I'm rather stumped. As I think, I'd use the current LwIP instance for building up the tunnel connection, and the application would use a second instance for the actual network communication, while the network interface of the second instance is a virtual one (like a tap device on linux), encapsulating its low level data and tranceiving it via the tunnel connection of the first LwIP instance.
Maybe this way I'd be able to create a custom solution for the problem, but the solution should conform to any standards (as the server will be any kind of sophisticated system).
So I wonder if anyone has been confronted with a task like this, and would appreciate any hint what to do, at least a direction where to look at.
Thanks in advance!
The short story: me and friend are making a multiplayer action game and we thought playn would be great for this. Android, java and HTML5 support is the most important ones but we don't want to cut out the others if not necessary.
The problem is now when we want to implement the networking part of it. We have implemented our own capable server and thought we would use long polling http requests for communication. We estimate now we need some way to have one thread running for the communication that use messages and two multithread safe queues. One queue for incoming messages that the update() part can consume from and one queue for outgoing messages to the server.
Is there any way to implement this without losing platform support? Or any other idea how we can implement this?
PlayN currently has no cross-platform support for persistent socket connections to a server. You will need to implement your own cross-platform abstraction. You can use WebSockets for the HTML5 backend, and you can look for a WebSockets library for Android and whatever other platforms you intend to support.
You can also use the Nexus library, which is designed to work with PlayN and provide client/server communication. However, it raises the level of abstraction substantially beyond passing simple messages between the client and server, so it might be easier to just implement your own simple WebSockets based communication than to learn how Nexus works.
I am building an app that sends information between two iPhones. The app is working great but the one problem I am having is that I have no way of telling whether bonjour is choosing wi-fi or bluetooth to make the connection. I would like to allow the user to be able to choose which they prefer. Also, is there way to programmatically tell is the device's bluetooth is on?
There is NO WAY TO TELL.
It's just one of those weird things.
And in fact there is no way to programmatically choose WiFi or Bluetooth. It's annoying but true.
Often, multidevice games will have a warning for users:
"Be sure to TURN OFF Bluetooth, to
ensure you are using your WiFi
connection."
That's the situation.
Bonjour is just a service discovery protocol - it doesn't care what kind of network you have. It will discover services across a mixture of networks (e.g. via bridges and routers), so it doesn't really make sense to try to map a service discovered via Bonjour to a single type of transport layer.
I'm developing a multi-player game and I know nothing about how to connect from one client to another via a server. Where do I start? Are there any whizzy open source projects which provide the communication framework into which I can drop my message data or do I have to write a load of complicated multi-threaded sockety code? Does the picture change at all if teh clients are running on phones?
I am language agnostic, although ideally I would have a Flash or Qt front end and a Java server, but that may be being a bit greedy.
I have spent a few hours googling, but the whole topic is new to me and I'm a bit lost. I'd appreciate help of any kind - including how to tag this question.
If latency isn't a huge issue, you could just implement a few web services to do message passing. This would not be a slow as you might think, and is easy to implement across languages. The downside is the client has to poll the server to get updates. so you could be looking at a few hundred ms to get from one client to another.
You can also use the built in flex messaging interface. There are provisions there to allow client to client interactions.
Typically game engines send UDP packets because of latency. The fact is that TCP is just not fast enough and reliability is less of a concern than speed is.
Web services would compound the latency issues inherent in TCP due to additional overhead. Further, they would eat up memory depending on number of expected players. Finally, they have a large amount of payload overhead that you just don't need (xml anyone?).
There are several ways to go about this. One way is centralized messaging (client/server). This means that you would have a java server listening for udp packets from the clients. It would then rebroadcast them to any of the relevant users.
A second way is decentralized (peer to peer). A client registers with the server to state what game / world it's in. From that it gets a list of other clients in that world. The server maintains that list and notifies the other clients of people who join / drop out.
From that point forward clients broadcast udp packets directly to the other users.
If you look for communication framework with high performance try look at ACE C++ framework (it has Java bindings).
Official web-site is: http://www.cs.wustl.edu/~schmidt/ACE-overview.html
You could also look into Flash Media Interactive Server, or if you want a Java implementation, Wowsa or Red5. Those use AMF and provide native functionality for ShareObjects including synching of the ShareObjects among connected clients.
Those aren't peer to peer though (yet, it's coming soon I hear). They use centralized messaging managed by the server.
Good luck