I have developed serve-client model based on UDP. Client are connected to server on random basis. I mean number of clients alive at a time is not fixed.
Any new client can communicate any time. It means, there could be 1 live client or 100 clients or any number of clients.
Now in such model, I need to add HTTP requests. Browser could send request to server and then server will forward that to any of client based on some identification.
Is there any method or readymade server(like nginix or lighttpd), which I can use for this requirement.
My big worry is that, destination client are not fixed, they keep changing. Most of server (nginix or lighttd) have static entries for destination address.
I visualize your scenario as multiple sensors that connect to the servers when they have something to say, and then they send a request and wait for the answer.
I visualize you also want to somehow administer such modules so that you want to access to them via HTTP.
You could leave the new configuration items on the regular server so that upon any update connection the response would include (in a piggy-backed fashion) the changes to the node.
Or the server could mark somehow your interest in accessing a certain node, and then, when this connects, the server could notify the interested client. The sensor should pay attention to clients wanting to connect to them during a window time.
Certainly, more information would help us help you.
Related
I have a configuration with the following server/clients :
One server with two bound sockets, a REP and a ROUTER
A client (we will call it a worker) that stays connected to the ROUTER socket
Another (real) client that connects on the REP socket.
I want the server to be able to tell the real client to connect (directly or somehow through the server) to a websocket, opened on the worker client. But it seems, I cannot retrieve the worker's IP-address from a ZeroMQ socket.
How could I achieve this, without some dirty IP-address retrieve hacks?
How could I achieve this, without some dirty IP-address retrieve hacks?
The best would be to use an explicitly communicated IP-address dialogue / handshaking between the server and the worker which would take place upon their setup / initialisation, in which the worker adviced these configuration details to server, upon having been asked to provide a such answer.
Given that, the "new"-real-client .connect()-s it's REQ onto the server's REP, and asks the server about where to go next, the server thus can answer this and the "new"-real-client will get received this way a legitimate IP-address:port# and any additionally needed details for any additional TCP/IP-L3 service establishment and use.
That simple :o) distributed-system
Design-side Epilogue:Because there are some further, design-side implications, hardwired inside of each type of the ZeroMQ sockets' Access-Point, it might be found more appropriate to serve a separate REP-AccessPoint on the server side, so as not to subordinate each "new"-real-client to become dependent upon a presence of events outside of the domains of control of both the server and such "new"-real-client, but to rather allow both such REQ/REP-endpoints to enjoy the independence of anything but their temporally (semi-)private details (re-)negotiation(s).
I have an ASP.NET Web API application running behind a load balancer. Some clients keep an HTTP busy connection alive for too much time, creating unnecessary affinity and causing high load on some server instances. In order to fix that, I wish to gracefully close a connection that is doing too much requests in a short period of time (thus forcing the client to reconnect and pick a different server instance) while at same time keeping low traffic connections alive indefinitely. Hence I cannot use a static configuration.
Is there some API that I can call to flag a request to "answer this then close the connection" ? Or can I simply add the Connection: close HTTP header that ASP.NET will see and close the connection for me?
It looks like the good solution for your situation will be the built-in IIS functionality called Dynamic IP restriction. "To provide this protection, the module temporarily blocks IP addresses of HTTP clients that make an unusually high number of concurrent requests or that make a large number of requests over small period of time."
It is supported by Azure Web Apps:
https://azure.microsoft.com/en-us/blog/confirming-dynamic-ip-address-restrictions-in-windows-azure-web-sites/
If that is the helpful answer, please mark it as a helpful or mark it as the answer. Thanks!
I am not 100% sure this would work in your situation, but in the past I have had to block people coming from specific IP addresses geographically and people coming from common proxies. I created an Authorized Attribute class following:
http://www.asp.net/web-api/overview/security/authentication-filters
In would dump the person out based on their IP address by returning a HttpStatusCode.BadRequest. On every request you would have to check a list of bad ips in the database and go from there. Maybe you can handle the rest client side, because they are going to get a ton of errors.
Write an action filter that returns a 302 Found response for the 'blocked' IP address. I would hope, the client would close the current connection and try again on the new location (which could just be the same URL as the original request).
My job is to write a distributed client/server application with some concurrent tasks. So i decided to use akka.net for the concurrency issues. To implement the ipc between server and client akka remote is used. For some reasons there may run more than one client of the same type on a workstation. So i configured these clients for dynamic assignment of a tcp port. This worked fine for sending messages to the server.
My problem is to push some information to the clients. To accomplish this task an actor on the client exist. Now the server creates a reference for this actor. Therefor it needs the port the client is listening on . My idea is to send the tcp port the client uses to the server in some sort of connection procedure using a actor on the server.
After searching for some hours I didn't find any hint where to find the dynamically assigned tcp port. So how would the client get the assigned tcp port?
Ok, I could use akka.cluster. But using akka.cluster is breaking a fly on the wheel, I think. And if it solves my issue reamins to be seen.
Two suggestions, assuming that it is your client that makes the first contact with the server.
I'd have the server keep track of which clients are connected. I'd probably have a heartbeat message that gets sent once every few seconds from each client system. This way you can store an IActorRef for each alive client and send messages back without the need for finding the port. IActorRefs are preferable wherever possible for location transparency.
If you actually need to explicitly find the port, you may be able to extract it from the Path property of the IActorRef of one of the actors on the client system.
Thanks to patricks suggestions my issue is solved.
The solution is to extract the needed information from the senders path available while executing the hello message. With this information the server is able to maintain a list of all connected clients and theire network address.
Thanks a lot # patrick.
Regards Gregor
I am trying to create a Web Server of my own and there are several questions about working of Web servers we are using today. Questions are:
After receiving a HTTP request from a client through port 80, does server respond using same port 80?
If yes then while sending a large file say a pic in MB's, webserver will be unable to receive requests from other clients?
Is a computer port duplex or simplex? (Can it send and receive at the same time)?
If another port on server side is used to send response to client, then (if TCP is used, which is generally used), again 3-way handshaking will be done which will be overhead...
http://beej.us/guide/bgnet/output/html/singlepage/bgnet.html here is a good guide on what's going on with webservers, although it's in c but the concepts are all there. This will explain the whole client server relationship as well as some implementation details.
I'll just give a high level on what's going on:
Usually what happens is when your server gets a new request that comes in it creates a fork that will process it, that way you are not bogged down by each request, when the request comes in the child process is handed a new file to write to(again this is all implementation details).
So really you have one server waiting for requests and for each request it received it spawns a child to process to deal with this request. I'm sure there are much easier languages to implement this stuff than c(I had to do both a c and java server serving to either one in my past) but c really gets you to understand the things that are going on and I'm betting that is what you are looking for here
Now there are a couple of things to think about:
how you want the webserver to work. The example explains the parent child process.
Do you want to use tcp/UDP there are differences in the way to payload gets delivered.
You don't have to connect on port 80. that's just the default for web.
Hopefully the guide will help you.
Yes. The server sends the response using the TCP connection established by the client, so it also responds using the same port. The server can handle connections from multiple clients using the same port because TCP connections are identified by (local-ip, local-port, remote-ip, remote-port), so the server can even handle multiple connections from same client provided that the source ports are different.
There are different techniques you can use to be able to serve multiple clients at the same time. These include
using multiple processes or threads: when one is busy serving a client the others can serve other clients.
using events: the server listens for events from the OS: when it can write a block of data to a connection it writes it, when a new client connects it accepts the connection, ...
Frequently both approaches are be combined.
A TCP connection is duplex: you can send and receive at the same time. The HTTP protocol is based on a simple request-response model though: at any given time only one party is "talking."
I'm working on a live client-server system using TCP. The system must ready 24/7 with cut-off time 30 minutes per day.
For some reasons like testing, I want to add some 'shadow servers' to the system, so that clients will send request to main server and shadow servers. While the request should be sent to all server, only the reply from main server that matters thus should be sent back to client. Reply from shadow servers should be ignored.
Moreover, starting and stopping shadows server mustn't do any harm to the system. If a shadows is up, it will receive request, if it's down, nothing will happen to client-main server.
Is there a way for me to do this without changing either client or main server code?
You can't do this in client or server code because TCP is point-to-point only.
Perhaps what you want is a "frontend load balancer" that keeps track of what servers are running and forwards incoming requests to one of those.
On the high end, a NetScaler does all this. Though I haven't personally configured one of these devices, I expect it can have both "primary" and "backup" servers. When I used them, it distributed the load evenly between many servers. It can also be arranged in "high availability pairs" where two of them are connected with one as a "hot standby" in the case where the primary fails.
You probably don't need anything this sophisticated but it serves to illustrate the point.