I try to create Asynchronous(non-blocking) request in my J2me application.
I write code as per this tutorial: Ajax-like Asynchronous SOA Calls with Java ME.
Code run successfully on emulator on Netbeans.
But when app deploy and device it fails on multiple connection.
When two connection open. then first connection tread kill and execute second only.
This problem only on device. It works fine on PC
According to this article http://developers.sun.com/mobility/midp/articles/mmapioverview/index.html "Note also that MIDP limits the number of HTTP connections open simultaneously to four.", but your device seems to only allow one connection.
In this case you should create a queue and execute one thread at a time.
Related
I'm writing a proprietary Telnet class and use TcpClient. Everything works well in the console and data transmission generates no issue with devices (sockets) in the same IP group. I tested also a new WPF project using this class again and the functionality is given as well.
Today I tried the identical WPF project again using a VPN connection, but TcpClient generates an exception. At the beginning it looks like the first console version was still working as expected, but during several tests, I noticed that even the console version generates sporadically an exception.
I checked the VPN connection and the availability of the IP/port. Everything should be fine. I used Wireshark (I’m not familiar with) and it looks like in the case, the connection fails, there is no request to the IP in the VPN network.
After a restart of the computer, connecting seems to work several times, but after a view tests, it ends with an exception again.
For sure, I have to handle the exception but first of all, I try to solve this connection issue.
Did anybody have experience using TcpClient and VPN? I read, that it’s sometimes recommended to use a bind, but till now, I don't have a solution.
This is a link to the console version I used as a starting point.
Is it possible to receive a list of all established connections in Swift like when using the "lsof" command?
I just saw that system calls (using Process) are not allowed in the Sandbox (which makes sense...).
I'd like to know if there's a way to communicate directly between two (or more) flask-socketio servers. I want to pass information between servers, and have clients connect a single web socket server, which would have all the combined logic and data from the other servers.
I found this example in JS Socket IO Server to Server where the solution was to use a socket.io-client to connect to another server.
I've looked through the Flask-SocketIO documentation, as well as other resources, however it doesn't appear that Flask-SocketIO has a client component to it.
Any suggestions or ideas?
Flask-SocketIO 2.0 can (maybe) do what you want. This is explained in the Using Multiple Workers section of the documentation.
Basically, the servers are configured to connect to a shared message queue service (redis, for example), and then a load balancer in front of them assigns clients to any of the servers in the pool using sticky sessions. Broadcasting operations are coordinated automatically among the servers by passing messages on the queue.
As an additional feature, if you use this set up, you can have any process connect to the message queue to post messages for clients, so for example, you can emit events to clients from a worker or other auxiliary process that is not a SocketIO server.
From your question it is unclear if you were looking to implement something like this, or if you wanted to have the servers communicate for a different reason. Sending of custom messages on the queue is currently not supported, but your question gave me the idea, this might be useful for some scenarios.
As far as using a SocketIO client as in the question you referenced, that shouud also work. You can use this Python package: https://pypi.python.org/pypi/socketIO-client. If you go this route, you can have a server be a client and receive events or join rooms.
I'd like to develop a simple solution using .NET for the following problem:
We have several computers in a local network:
10 client computers that may need to execute a program that is only installed on two workstations
The two workstations that are only used to execute the defined program
A server that can be used to install a service available from all previously described computers
When a client computer needs to execute the program, he would send a request to the server, and the server would distribute the job to a workstation when available for execution, and inform the client computer when the execution has been performed.
I'm not very used to web and services development so I'm not sure if it's the best way to go, but below is a possible solution I thought about:
A web service on the server stores in queues or in a database the list of tasks with their status
The client computer calls the web service to execute a program and gets a task id. Then calls it every second with the task id to know if the execution has been performed.
The workstations that are available call the web service every second to know if there is something to execute. If yes, the server assigns the task, and the workstation calls the web service when the execution is completed.
I summarized this in the below figure:
Do you think to a simpler solution?
Have a look at signalr! You could use it as messaging framework and you would not need to poll the service from 2 different diretions. With signalR you would be able to push execution orders to the service and the service will notify the client once the execution has been processed. The workstation would be connected with signalR, too. They would not need to ask for execution orders as the webservice would be able to push execution orders to either all or a specific workstation.
I need to build a Windows Service in VB.net under Visual Studio 2003. This Windows service should read the flat file (Huge file of about a million records) from the local folder and upload it to the corresponding database table. This should be done in Rollback mode (Database transaction). While transferring data to table, the service should also be listening to additional client requests. So, if in between client requests for a cancel operation, then the service should rollback the transactions and give feedback to the client. This windows service also keeps writing continuously to two log files about the status and error records.
My client is ASPX page (A website).
Can somebody help me explain how to organize and achieve this functionality in a windows service(Processing and listening for additional client requests simultaneously. Ex. Cancellation request).
Also could you suggest me the ideal way of achieving this (like if it is best to implement it as web service or windows service or just a remote object or some other way).
Thank you all for your help in advance!
You can architect your service to spawn "worker threads" that do the heavy lifting, while it simply listens for additional requests. Because future calls are likely to have to deal with the current worker, this may work better than, say, architecting it as a web service using IIS.
The way I would set it up is: service main thread is listening on a port or pipe for a communication. When it gets a call to process data, it spawns a worker thread, giving it some "status token" (could be as simple as a reference to a boolean variable) which it will check at regular intervals to make sure it should still be running. Thread kicks off, service goes back to listening (network classes maintain a buffer of received data so calls will only fail if they "time out").
If the service receives a call to abort, it will set the token to a "cancel" value. The worker thread will read this value on its next poll and get the message, rollback the transaction and die.
This can be set up to have multiple workers processing multiple files at once, belonging to callers keyed by their IP or some unique "session" identifier you pass back and forth.
You can design your work like what FTP do. FTP use two ports, one for commands and another for data transfer.
You can consider two classes, one for command parsing and another for data transfer, each one on separate threads.
Use a communication channel (like a privileged queue) between threads. You can use Syste.Collections.Concurrent if you move to .NET 4.0 and more threading features like CancellationTokens...
WCF has advantages over web service, but comparing it to windows service needs more details of your project. In general WCF is easier to implement in compare to windows service.