Hi peeps, hopefully this is the right place to ask this question. I just discovered zmq a couple of days ago while trying to find a networking/message sending solution, and have been reading through the docs and guide. I'm trying to wrap my head around/better understand how to use the different socket types to solve certain scenarios, and was wondering if someone with experience could give their opinion/feedback?
The specific scenario is something like the following (I'm going to make up a scenario related to camera video streams in a house, just to be more concrete):
- A single server, which has video streams of multiple rooms of a house (kitchen, living room, etc).
- At any point, a number of clients can connect to the server and request one or more streams from the server. So one client might connect and say, I want the stream of the kitchen and the living room. As is typical for video streams, this does not have to be reliable, but (and this is critical), this stream must be as low latency as possible. Every millisecond counts. This is priority zero, and why I am even looking at switching networking solutions, the current one is too slow.
- The relationship is not so unidirectional, however, as in addition to simply receiving data, a client can also send messages to the server, telling it to, say, move the camera in a room, but only if they are actually streaming the video for that room. These messages are small, infrequent, but should be reliable. Latency not critical here.
- There are also infrequent, reliable, latency uncritical messages that the server sends to the client.
That roughly sums up the scenario. What I've come up with:
- Client-Server pattern for initial handshake/connections, as well as all client->server communication, and all reliable server->client communications.
- Radio-Dish pattern for the streams
So roughly, something like this:
A client sets up a ZMQ_CLIENT socket, connects to the server, says they want the "kitchen" stream. The server sets up the ZMQ_RADIO socket (if this is first client, otherwise already exists) and the group, and sends the group name to the client. The client then sets up a ZMQ_DISH socket, and begins receiving the stream.
Does this seem like I am following the patterns that zmq sets up in an intended way? If not, any feedback?
Don't share ZeroMQ sockets between threads. ZeroMQ sockets are not threadsafe, while the documentation says Following are the thread safe sockets: * ZMQ_CLIENT * ZMQ_SERVER * ZMQ_DISH * ZMQ_RADIO * ZMQ_SCATTER * ZMQ_GATHER. These all look like newer/draft socket types, so is it just that the newer ones have been implemented in thread safe manners while the older ones have not?
@sappo Thanks for your help, i'll have to take a look at that. And if you helped write the ZeroMQ guide, you did do an excellent job. It's definitely one of the easier texts i've read
I guess i'm trying to determine if i need a protocol or not. Basically i have 1 client (Router Socket) that needs to send a request to one specific server, with a dealer socket, (There are several servers) to perform some work then send the result back to the client. I figure the router socker can prepend an ID to the message and send it to the specific client. What scenarios would i have to write my own protocol?