I am trying to turn the server/client model into a server/server model, so as to have the my 2 computers running the program find each other by perhaps a url or something else like ip address.I was wondering if it was possible for 2 servers to connect via url's. or is ip the only way? examples would be appreciated since this is my second day writing c++.
For HTTP, the server only talks to clients. So, I am not sure what you mean by server to server.
URLs are fine to use to access an HTTP server, but the host name will need to be resolved into an IP address before a network connection can actually be established. You should be able to find libraries that will do those details for you, but it is not hard to manually establish a socket connection to an HTTP server.
There are configurations where there are multiple servers, acting as a single server. These are sometimes referred to as web farms or a HTTP cluster. Typically, there is some sort of load balancer in front of the cluster. Many HTTP load balancers support a server affinity feature to make sure a client is sent to the same server in the cluster for subsequent operations.
In a cluster configuration, servers may need to synchronize shared state, such as file system data or configuration data. This is typically handled by some mechanism that is external to the HTTP server process itself. The HTTP server process may need to cooperate with the synchronization, but this can be as simple as restarting the process.
There is another mode of HTTP server configuration called a reverse proxy configuration. A cluster of HTTP proxy servers sit in front of a single HTTP server. The proxy servers are thought to be cheap and expendable entities that off load work from the HTTP server itself, providing a scalable means to increase HTTP server capacity.
There are many open source HTTP server and proxy projects available as examples of how they are implemented. If you are trying to build your own custom server application, you can have a look at the HTTP examples in Boost asio.
Related
Is it possible to use AWS Application Loadbalancer for RSocket?
An AWS Application Loadbalancer can also be used for WebSocket connections and my project uses RSocket with WebSocket as its transport. This made me wonder if it is possible to use this loadbalancer for RSocket aswell.
On one hand I would think it is possible to use this loadbalancer, as it only receives a connection and passes this to the target RSocket server.
On the other hand, if all RSocket frames go through the loadbalancer, it might not know how to handles these frames, which would make it not possible to use.
I couldn't find much about RSocket and loadbalancing online besides this post .But this is client side loadbalancing and I was looking for server side loadbalancing.
And this post .But this uses LoadBalanceSocketClient while I want to find out if an AWS Application Loadbalancer can be used.
Here follows a simple diagram of what I would like to have (if possible):
The RSocket client connects to the loadbalancer which passes the connection to a RSocket server (for example server A). Then the client and RSocket server A can communicate.
AWS will see this as a typical websocket service. So as long as it lets HTTP/1.1 connections through and lets them upgrade to WebSocket there shouldn't be a problem. This is very standard so it shouldn't be an issue. Ideally it won't see individual frames of the traffic, and you app will handle all frames on a single WebSocket connection. But it looks like the API Gateway support does deal with individual messages https://docs.aws.amazon.com/apigateway/latest/developerguide/apigateway-set-up-websocket-deployment.html. You should ignore the RSocket client load balancing, and focus on AWS WebSocket routing.
As an example, with GCP (instead of AWS) the complexity is that this bumps you up from AppEngine Standard to Flexible. The demo site https://demo.rsocket.io/ is deployed to GCP and exposes websockets.
The additional kink, is that you possibly want stateful routing if you want client resumption.
I was hoping someone may be able to explain how I would setup a multi-tiered web application. There is a database tier, app tier, web server tier and then the client tier. I'm not exactly sure how to separate the app tier and web server tier since the app tier will be in a private subnet. I would have the client send the request directly to the app server but the private net is a requirement. And having the app server separated from the web server is a requirement as well.
The only idea I have had was to serve the content on the web server and then the client will send all requests to the same web server on another port. Like port 3000, if a request is captured on that port, a node app using express will forward the request to the app tier since the web server can speak to the app server.
I did setup a small proof of concept doing this. The web server serves the content, then I have another express app setup to listen on port 3000, the client sends the request on port 3000 and then it just sends the exact same thing back to the app server.
This is my current setup with the web servers hosting two servers. One to serve the frontend on port 80 and one to receive requests on port 3000. The server listening on port 3000 forwards all requests to the app server ALB(It's basically a copy of all the same routes on the app server but it just forwards the requests instead of performing an action). But is there a way to not have this extra hop in the middle? Get rid of the additional server that is listening on 3000 without exposing the internal ALB?
To separate your web servers and application servers, you can use a VPC with public and private subnets. In fact, this is such a common scenario that Amazon has already provided us with documentation.
As for a "better way to do this," I assume you mean security. Here are some options:
You can (and should) run host based firewalls such as IP tables on your hosts.
AWS also provides a variety of options.
You can use Security Groups, which are statefull firewalls for your hosts
You can also use Network Access Control Lists (ACLs), which are stateless firewalls used to control traffic in and out of subnets.
AWS would also argue that many shops can improve their security posture by using managed services, so that all of the patching and maintenance handled by AWS. For example, static content could be hosted on Amazon S3, with dynamic content provided by microservices leveraging API Gateway. Finally, from a security perspective AWS provides services like Trusted Advisor, which can help you find and fix common security misconfigurations.
I have deployed an application hosting Kestrels server bindded to a specific port as web job .I want to access that port in order to have to access to APIs implemented in that application.
If I try to bind with port 443 it fails on other ports the server starts but cant interact with external requests.Is there any way I can expose this port to listen to incoming requests
Azure Web App only support port 443 and 80. And webjob host in Azure App Service.
After a lot of searching for information and trying. I can tell you with certainty that other ports cannot be used.
For more details, you can read below post.
Opening ports to Azure Web Job
Is it possible to use an Azure Web Job to listen on a public socket
The above is a statement of port restrictions in webjob.
For you want webjob to monitor and process incoming requests, my suggestion is that webjob monitors ports 443 and 80 instead of binding. You can use RawSocket.
Monitor all requests, analyze whether the request content contains instructions that need to be executed, and then proceed to the next business operation.
If you already have completed project, you also can choose VM or Cloud Services.
I'm trying to implement a system using multiple servers which communicate with the clients via TCP. As there are going to be multiple backend servers to process clients' requests, I'm wondering if there exists a load balancing mechanism which after the load balancer receives a client request, it connects the client directly to a backend server so that they establish a two-way TCP connection and all future communication between the two is done directly between them and not through the load balancer.
In general terms, no, IP doesn't allow this, individual connections cannot be handed off to other machines. The protocol does not permit it. You can, in the case of high-availability, hand off all connections from one machine to another, but even that is kind of a hack and is done using MAC address shifting.
What you want is probably something like HAProxy which is a TCP/IP load balancer. It's fast enough that being in the middle isn't really a problem, you won't feel a performance hit.
The alternative is to do something in the application layer where your "load balancer" tells clients which server to connect to, but doesn't actually do the connecting. That's done by the client in a secondary request. Sometimes this is done via DNS, sometimes via time-limited tokens to ensure clients respect the routing.
I am trying to setup an Elastic load balancer to route requests to a cluster of node.js servers running Primus.io with sockjs to manage real time communications.
I have set up the load balancer to listen with the following configuration:
HTTPS 8084 -> HTTPS 8084 (The port used on my node.js servers)
SSL 443 -> TCP 80
My understanding is that the only way to get websockets to work through ELB is via SSL->TCP, hence the above configuration.
I have correctly enabled the new proxy protocol for ELB as described here:
http://docs.aws.amazon.com/ElasticLoadBalancing/latest/DeveloperGuide/enable-proxy-protocol.html
When trying to connect to the server from a client an HTTPS request is initially sent and then from what I can gather it should be upgraded to websockets. But the request is simply failing when I send it to the loadbalancer address.
If I send the initial Primus connection request to the ip of a single nodejs server like so:
var primus = new Primus('https://ip.address.of.single.server:8084');
The request is correctly returned and is upgraded to websockets correctly.
When I switch the ip address to that of the balancer, it fails and the initial https request to the node.js server returns nothing. I assume this means that the websocket transfer could not be established, but to be honest I have little experience in this area so could be completely wrong.
Does anyone have any idea what I am doing wrong?
Thanks in advance
Do you have clustered your NodeJS-instances? For example, if you use SocketIO you should use a clustered session store. Actually, I'm also currently investigating the same with SockJS running on top of Vertx.
The problem behind is Amazon ELB won't respect any forwards in the past (in opposite to Sticky Session on top of HTTP) which means that a connections via TCP level can be forwarded at any cluster's node. Yes, one tcp channel would be okay. But frameworks like SocketIO do a little bit more to support sessions (does not exist in WebSockets) and multiple transport layers (http, polling, sockets, and so on).