I have many linux servers (cluster) to run my application.The application use C/S structure,client connect to server using TCP long connection(server is basing apache mina socket framework).
my question is : When one server shutdown, how other servers can keep the socket connection established between the failure server and the clients?
so the server-down failure can be transparent to clients and clients need not reconnect to server.
Thanks
L.J.W
You cannot simply migrate a TCP connection unless there is some kind of never-failing proxy in between like a layer-4-switch.
Related
I have a nodejs TLS client socket on my laptop, connected to a TLS server socket on a different computer (server). The server cannot connect to my laptop. The laptop needs to initiate the connection.
Now I want the server to make requests to my laptop. The idea is to reuse the HTTP protocol. Is there a way to create a HTTP server using the existing TLS client socket?
This way, the server machine can make a HTTP request, and the client TLS receives it, and the HTTP server would parse it? Or am I missing something?
Once you have a TCP socket open between laptop and server, you can send data either way over that socket. So, if the server wants to send some query to the laptop, it can do so just fine. You will have to invent your own protocol on top of TCP to do that, but it could be as simple as a text/line based protocol if you want.
Or, instead of making a plain TCP connection, you can make a webSocket or socket.io connection from the laptop to the server (instead of the plain TCP connection) and then either side can send messages either way and the protocol part is already taken care of. If you use socket.io, it will automatically reconnect if the connection is interrupted too.
There is no simple way to attach an HTTP server to an existing TCP socket and it would be fraught with difficulties too because an HTTP connection is generally not a continuous connection over which you send many separate requests (advanced versions of http can do that, but I doubt you want to get into implementing all that logic on both ends). You could use the HTTP protocol over your existing TCP socket, but that would probably be substantially more work to implement than just use the webSocket/socket.io idea above.
I have a tcp server running. A client connects to the server and send packet periodically. For TCP server, this incoming connections turns to be CONNECTED, and the server socket still listens for other connections.
Say this client suddenly get powered off, no FIN sent to server. When it powers up again, it still use the same port to connect, but server doesn't reply to SYNC request. It just ignores incoming request, since there exists a connection with this port.
How to let server close the old connection and accept new one?
My tcp server runs on Ubuntu 14.04, it's a Java program using ServerSocket.
That's not correct, a server can accept multiple connections and will accept a new connection from a rebooted client as long as it's connecting from a different port (and that's usually the case). If your program is not accepting it it's because you haven't called accept() a second time. This probably means that your application is only handling one blocking operation per time (for example, it might be stuck in a read() operation on the connected socket). The solution for this is to simultaneously read from the connected sockets and accept new connections. This might be done using an I/O multiplexer, like select(), or multiple threads.
What is the difference between Web sockets per instance and IP connections?
Reference: https://learn.microsoft.com/en-us/azure/azure-resource-manager/management/azure-subscription-service-limits#managing-limits
WebSocket protocol enables a full duplex communication between a server and a client over a long running TCP connection. In a simple word, WebSocket uses TCP/IP to communicate.
I have an application server which is listening for Tcp connection. The clients connecting to this application establish persistent connection with Tcp keepalive. Once in a while I would see that the client finds it has lost connection but the application server isn't aware of it.
I did see high cpu on application server once but I am not sure if it is correlated. Also there was no issue with the network.
Can this be because application server didn't reply to tcp keepalive probes and hence client disconnected?
I have to implement a server to server communication protocol using a SINGLE PERSISTENT TCP connection. The server at both the ends of this connection are implemented using "multi-threaded and asynchronous event-driven model". Both these servers are implemented in C++ and Pthreads on Linux. Server A always sends requests to Server B and Server B responds with a response. Server B doesn't send any requests to Server A, it just responds to the requests it receives. Could some one post me a sample code for this communication? Could you help me with the code for both Server A and Server B? Or please point me to any old answers or any websites where i can find a prototype code. Thanks in advance.
TCP servers cannot open connections to TCP servers. There is no IP protocol for that. One of the two servers must run a TCP client as a subsystem. The exact mechanics of how you do that depend on your client<>server protocol - the 'server-client' could log in to the 'client-server' with a unique username/password, or could use a different server listening port.
It's up to you:)