I am writing a server and client code where i want to identify on server side official client software sending data.
The protocol is text based, so anyone can write it's own client - and i want to keep it, but want to group the devices by "Official" / "Non Official" based on the 'fingerprint' of my official client application.
Question:
How can i filter out my clients from other clones sending?
I am thinking to send encrypted message from my client to SERVER using the same key, so once decoded if it's valid, then i know its my app code sending - but before i go this way, any other better ideas ?
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I am making an application in C++ for Windows, which consists of a Client and a Server. The Server manages the Device.
The Client sends to the Server commands like:
Start Device
Stop Device
Set Device Gain
Set Device bandwidth
Get Device status
Data must be transferred from the Device to the Client for display on the screen. Data is arrays of complex numbers. There will be a lot of data, since there can be several Devices.
I developed my own command format, which is converted to JSON and then to a string.
I'm having a hard time choosing a template for ZeroMQ sockets. For data transfer, I chose the PUB-SUB pattern: the Server is the Publisher, and the Client is the Subscriber.
For sending commands, I also chose the PUB-SUB pattern, but in this case the Client is the Publisher, and the Server is the Subscriber.
In both cases, all messages received by the Subscriber are queued and further parsed.
This approach is very primitive. Perhaps you can suggest me more advanced templates? It would be great with sample code for Client and Server.
I am trying to write a simple client-server application where a client can send or broadcast a message to one or all clients in the network. The server stores all IP addresses that are connected to it, and broadcasts a new IP if a new client connects itself.
I'm not quite sure how to implement the sending of a single message to another client. Would I just have to send a TCP message to the server and put the desired recipient as data in the TCP layer which is then extracted by the server so it knows where to send it?
I also want to add encryption to the messages which would then no longer allow the server to read the data, so I'm not sure how to solve that!?
I am using c++ and Qt5 for the implementation
I'm not quite sure how to implement the sending of a single message to
another client. Would I just have to send a TCP message to the server
and put the desired recipient as data in the TCP layer which is then
extracted by the server so it knows where to send it?
In an ideal world, the clients could talk to each other directly, since they could find out the IP addresses of the other clients from the server (either via its broadcast or by requesting a list of IP addresses from the server). If all of your clients are running on the same LAN, that can work well.
Assuming you want your system to run on the general Internet, however, that won't work so well, since many/most clients will be behind various firewalls and so they won't accept incoming TCP connections. (There are some ways around that, but they require a very advanced understanding of how TCP works, and even then they only work in certain situations, so I don't recommend attempting them in a first project)
Therefore, for a reliable client->client messaging mechanism, your best bet is indeed to have the sending client send the message to the server, along with some short header that tells the server which other client(s) the message ought to be forwarded to. My own client/server messaging system works along these lines, and I've found it to work well.
I also want to add encryption to the messages which would then no
longer allow the server to read the data, so I'm not sure how to solve
that!?
Don't worry about adding encryption until you've got the basic non-encrypted functionality working first, since encryption will make things much more difficult to debug. That said, it's perfectly possible to pass encrypted/opaque data to the server, as long as the aforementioned header data (which tells the server where to forward the message to) is not encrypted (since the server will need to be able to read the header to know what to do with the encrypted data). The trickier part will be when the receiving client gets the forwarded data from the server -- how will the receiving client know how to decrypt it? You'll need some external mechanism for clients to share keys (either symmetric keys or public/private keypairs), since if you sent the encryption keys themselves through the server, there wouldn't be much point in encrypting anything (since the server could retain a copy of any keys it forwarded, and use them to decrypt, if it wanted to)
I need to do some validation testing of a new feed handler I have made. I have some pcap data that I captured from the production network and I would like to have my development feed handler connect to the "replay" of this data and compare the results.
My pcap:
I have a prod application that connects to a data feed, a TCP connection to an external server lets call assume this is 123.456.789.1:1234. This external sever then sends data to my application there is almost no client to server communication the server just sends the client data until the client drops. I have a pcap of all the packets sent to and from port 1234. I got this pcap by mirroring the production port (SPAN) on the switch and attaching tcpdump to an interface plugged in to the mirrored network port. When I look at the PCAP in wireshark it has all the data I would expect.
My problem:
I am in no way a network engineer and I am unsure how I can use this pcap to test my application. What I would like to do is "replay" this stream form the pcap and connect to it with my development application to validate that the data is being handled the same was it was on the prod connection.
I would like to some how "replay" the data sent from 123.456.789.1:12344 on 127.0.0.1:1234 and then connect to 127.0.0.1:1234 with my dev application. I looked at tcpreplay but from the documents I can not seem to figure out if it can do this, I get the feeling that they do not handle the tcp session data, and I could do this if it was a UDP stream, but tcpreplay can not act as the external server. Did I read this wrong or is there another tool that will let me do this?
thanks!
You may want to use netcat if you just want to throw some data back at your tool, and you don't care about what the tool sends.
You would do this by extracting the raw data sent by your tool from the pcap file (this tool may be helpful) and then piping that into netcat.
Well...
I am working with an mobile application and a web server.
A characteristic of my web server is that it generates different set of data randomly. In other words, I cannot predict when the server will have ready data to send to the mobile app.
On other hand, the mobile app need to receive all data that the server generates. An approach could be request multiple times to get all these data. Indeed, It isn't a good approach, because I don't know when request the data.
If the mobile app could listen the server, after one start request or keep on the connection, for example, the server could sent any set of data in any time.
The question is: What is protocol suitable to this situation? How could I use that? Examples?
Thank you!
You could create a persistent TCP/IP connection to the server and permanently listen for incoming data (using a custom protocol or propably something websocket based). However such a permanent connection might seriously affect your battery life if it's for a mobile device. You will also lose the connection if the operating system automatically shuts down your application because it's out of memory.
The default approach to this problem are Push notification / Push services, where your server sends a notification about new data to a server of the phone provider (e.g. Microsoft or Apple push server), and this server sends the notification (as well as notificaiton from other online services) to your phone.
Some info for Windows Phone:
http://msdn.microsoft.com/en-us/library/hh221549.aspx
http://msdn.microsoft.com/en-us/library/windowsphone/develop/ff402558%28v=vs.105%29.aspx
Depending on how often you have new data both approaches can make sense.
WebSockets could be the answer: http://en.wikipedia.org/wiki/WebSocket
Specifically, for Windows Phone, there's a solution also: http://msdn.microsoft.com/en-us/library/windowsphone/develop/ff402558(v=vs.105).aspx
Can someone give me some hints on using http progressive download in non http applications. I need to stream some video frames to a client application and display them. I need to develop the server side application and the client side application. I presume that the server side isn't too hard( I just receive a request and start transferring ). The client side is the problem for me. How can I approach this problem with regards to:
caching ( need some sort of caching in file )
indexing( the user must be able to salt to a specific time )
clean up( when to discard the file )
Shortly, I need an application in C++ that replicates the behavior of flash player.