I currently have a Java Applet running on my web page that communicates to a display pole via COM1. However since the Java update I can no longer run self-signed Java Applets and I figure it would just be easier to send an AJAX request back to the server and have the server send a response to a TCP port on the computer...the computer would need a TCP > COM virtual adapter. How do I install a virtual adapter to go from a TCP port to COM1?
I've looked into com0com and that is just confusing as hell to me, and I don't see how to connect any ports to COM1. I've tried tcp2com but it doesn't seem to install the service in Windows 7 x64. I've tried com2tcp and the interface seems like it WOULD work (I haven't tested), but I don't want an app running on the desktop...it needs to be a service that runs in the background.
So to summarize how it would work:
Web page on comp1 sends AJAX request to server
Server sends text response to comp1 on port 999
comp1 has virtual COM port listening on port 999, sends data to COM1
pole displays data
EDIT: I'm using Win 7 x64 and tcp2com doesn't work as a service. I tried using srvany but I get an error stating that the application started then stopped. If I use powershell and pass the tcp2com as an argument, it doesn't quit but it also doesn't run. So I nixed the whole 'service' deal and put the command: powershell -windowstyle hidden "tcp2com --test tcp/999 com1" and it works...sort of. The characters that get sent are all effed. I can write "echo WTF > COM1" on another computer which has COM2TCP (different vendor) and it'll come up as a single block on the POS display pole. However if I use COM2TCP on both the server and client machines, everything works fine...but that's only a trial version and it costs several hundred dollars! On another note, is there a way to send the raw text over IP without having to use another Virtual COM > IP adapter on another computer? Sort of like how curl works but different...?
After somewhat of an exhaustive search, I came across a program called 'piracom'. It's a very simple app that lets you specify port settings for the express purpose of connecting a serial port to an listening port over the network. So this is IP > Serial. For Serial > IP I used HW-VSP3-Single as even on the piracom website it said it's compatible! I've tested and it works!
I just put a shortcut to piracom in the startup folder of my user account; the app runs off of a .ini that it updates every time you make a change...so if you run the server and hide it, on the next reboot of the pc it'll start up running and hidden with all prior settings. Easy.
Now it's a matter of installing HW-VSP3 on the server and making a method on the Rails app which will write to the virtual COM port. The only issue I can see right now is that writing echo \14Test This! > COM3 actually prints the \14...if I do that in my Java applet, it sends the "go to beginning" signal.
Addendum 1: The \14 problem was fixed by using the serialport gem for RoR. I created a method in a controller that returned head :no_content and then send data to the COM port. Calls to this method were made via jQuery's $.Ajax, using "HEAD" HTTP method. Apparently though I had to add the GET verb in Rails routes because the HEAD option isn't supported for some gimpy reason.
Addendum 2: Some garbage data was being sent to the display pole at the end of the string...turns out I needed to turn off the "NVT" option in HW-VSP3. Also keep in mind that firewalls need to be modified to allow communication.
Related
I have a setup where I use Flask-MQTT to connect my python Flask API to a Mosquitto broker. Whenever I run the Flask API with the development server all is well. But whenever I spin it up for production (using wsgi+nginx), the connection with Mosquitto is made, but everytime i try to publish something i get the following error:
Socket error on client <unknown>, disconnecting.
My app.ini has the processes configured to 1 (processes = 1)
My mosquitto.config has the allow_anonymous flag set to trye (allow_anonymous true)
I can't really seem to figure out what I'm doing wrong here...
Update:
So what i think is happening is that the Flask-uwsgi application is trying to connect to mosquitto more than once. There is a master process that connects with Mosquitto on initialize. Then there is a second process that is being used whenever input is given on the Flask app. I'm not sure, but I think Mosquitto only wants one connection at the time, therefor erroring on the second. So now i either need to:
A) Configure Mosquitto in a way that it accepts multiple connection from the same device
B) Configure Flask in a way that wil only use one single process (configuring processes = 1 is not enough, it will still spawn two processes)
99% of the time, a "Socket error on client <unknown>" is an authentication error. I don't know Flask, so I don't know where to point you at, but something in your code is either trying to pass a username/password that is not defined to Mosquitto, or its trying a TLS connection with an cert that Mosquitto doesn't like.
Alright, it turns I could've read that the whole multiple processes wouldn't work from the start at the official Flask-MQTT documentation. It sais right there in think letters:
Flask-MQTT is currently not suitable for the use with multiple worker
instances.
So I looked at my uwsgi app.ini file again closely and actually the answer is quite simple. I turned out i had a like in there master = true.. after I removed that it works like a charm.
I got the above error when try to connect two soft phones which is successfully registered. I was trying to make a voice call in local not connecting and instead returns the error:
chan_sip.c:4274 __sip_reliable_xmit: Serious Network Trouble; __sip_xmit returns error for pkt data
I am using asterisk 13.5.0 and not using freepbx. Simply try to make a call between two peers
Make changes to sip.conf edit the line bind address like bindaddr=0.0.0.0
Likly firewall or permissions(for socket) issues.
Solved
OK I've just solved this issue in my network.
First of all , about the situation : i had an "Issabel VoIP server" based on Asterisk 13 but when i wanted to make calls ,it just failed and i got the same error as yours on Asterisk CLI. I had successful ping requests from the server and extension had been registered without any errors.
Solution: I had doubt about network devices, so i installed 2 soft-phones (like 3cx or Zoiper) on my laptop and connected it straightly to the server using a LAN patch cord ( to see if there's an issue on server side or its related to my network infra.) and registered 2 extensions on my soft-phone and they called each other without problem.so i understood that its one of my network devices that was limiting the transition of VoIP packets between server and extensions . finally i got that it was my TDD-LTE Modem that intercept my connection.
So to make long story short :
1- First create a small network between your server and laptop
2- Register 2 extensions on your soft-phone
3- make call between them and if it goes fine , then look for an obstacle in your main network.
hope it could help you
I would want to send a message from the server actively, such as using UDP/TCPIP to a client using an arduino. It is known that this is possible if the user has port forward the specific port to the device on local network. However I wouldn't want to have the user to port forward manually, perhaps using another protocol, will this be possible?
1 Arduino Side
I think the closest you can get to this is opening a connection to the server from the arduino, then use available to wait for the server to stream some data to the arduino. Your code will be polling the open connection, but you are avoiding all the back and forth communications to open and close the connection, passing headers back and forth etc.
2 Server Side
This means the bulk of the work will be on the server side, where you will need to manage open connections so you can instantly write to them when a user triggers some event which requires a message to be pushed to the arduino. How to do this varies a bit depending on what type of server application you are running.
2.1 Node.js "walk-through" of main issues
In Node.js for example, you can res.write() on a connection, without closing it - this should give a similar effect as having an open serial connection to the arduino. That leaves you with the issue of managing the connection - should the server periodically check a database for messages for the arduino? That simply removes one link from the arduino -> server -> database polling link, so we should be able to do better.
We can attach a function triggered by the event of a message being added to the database. Node-orm2 is a database Object Relational Model driver for node.js, and it offers hooks such as afterSave and afterCreate which you can utilize for this type of thing. Depending on your application, you may be better off not using a database at all and simply using javascript objects.
The only remaining issue then, is: once the hook is activated, how do we get the correct connection into scope so we can write to it? Well you can save all the relevant data you have on the request to some global data structure, maybe a dictionary with an arduino ID as index, and in the triggered function you fetch all the data, i.e. the request context and you write to it!
See this blog post for a great example, including node.js code which manages open connections, closing them properly and clearing from memory on timeout etc.
3 Conclusion
I haven't tested this myself - but I plan to since I already have an existing application using arduino and node.js which is currently implemented using normal polling. Hopefully I will get around to it soon and return here with results.
Typically in long-polling (from what I've read) the connection is closed once data is sent back to the client (arduino), although I don't see why this would be necessary. I plan to try keeping the same connection open for multiple messages, only closing after a fixed time interval to re-establish the connection - and I hope to set this interval fairly high, 5-15 minutes maybe.
We use Pubnub to send notifications to a client web browser so a user can know immediately when they have received a "message" and stuff like that. It works great.
This seems to have the same constraints that you are looking at: No static IP, no port forwarding. User can theoretically just plug the thing in...
It looks like Pubnub has an Arduino library:
https://github.com/pubnub/arduino
The client use ssh login and start up a server on remote machine, then the clinet create a tcp connect to the server.
The server need exit when the client has exit normally or crashed or network is dropped.
So the question is how to detect if the client which the server has connected to is crashed.
The first try is using error() signal, catch QAbsoluteSocket::NetworkError to determine the network has dropped. But I can't receive error() signal at all even if i pull out the network cable.
The second try is using the SocketState, i think whenever SocketState is UnconnectedState,the client may has exit normally and the server should exit too. This way works fine for "normal exit", but I don't know how to deal with "crash" and "dead network".
Help me, thanks!
I'd recommend using TCP keep alive. It is not exposed through the public QTcpSocket interface, but you can use setsockopt with QAbstractSocker::socketDescriptor to activate the SO_KEEPALIVE feature.
EDIT: It appears that keep alive was added to QAbstractSocket at some point. So, simply call QAbstractSocket::setSocketOption with QAbstractSocket::KeepAliveOption.
You can find information about adjusting the timeout of keep alive request here: http://www.gnugk.org/keepalive.html
Most of the time, the only way you will know there is a problem with a socket connection is when you try to read or write with it. There are some exceptions: Windows will change the state of sockets if the network cable is unplugged, Linux (in my experience) will not.
The most reliable way to detect connection problems is to have the client regularly send a small message at an agreed upon interval with the server. If the server does not see this message within a reasonable time, it should consider the client dead and drop the connection. This will also give both sides regular opportunities to detect a problem via reads and writes.
I am trying to open the COM1 port but I am getting this error message "Access to the port 'COM1' is denied". I am writing a program for sending SMS via .NET. I expect there could be an error, but the error "Access denied" should not be arisen. Please give me any solution. If port requires any access privileges then how can I do that?
First, make sure the serial port exists. Check the Device Manager; right-click on My Computer, select "Manage" from the context menu, select "Device Manager", expand "Ports Com & LPT". If Com1 is not listed, you will need to enable it in the BIOS.
If COM1 is there, then another program has left it open. Access to COM1 is exclusive; only one program can have it open at a time. Fax software or a modem could have it open, or you could have left it open yourself.
This is easy to do. If you work on a program that opens the port and forget to close it, or if an error occurs and the program terminates without closing the port, this is the message you will get the next time you try to open COM1. Only the program that opened the port can close it. "Catch" or "Finally" blocks are good places to close the port and prevent this.
There's probably something else using COM1 (auto sync programs tend to be quite bad at grabbing COM ports as soon as they become available).
Try downloading PortMon and it will tell you exactly what's using the port.
Since you tagged this asp.net, are you trying to access the port with multiple threads? (as in on a request, accessing the port, creating the connection, sending data, closing connection, closing the port?
If you are, this is also a problem. If I am not mistaken, only one thread can access a com port at a time. You will need to write some code to ensure that only one thread is trying to access the port at a given time. Typically I would suggest a queue and a worker for that queue that does the job.
There is probably another program using the serial port. Have you tried firing up hyperterminal?
If you are trying to use ASP.Net under IIS there account running the website may not have permissiongs to the device, as well as, there could also be conflicting thread/multi-access issues. Something to consider would me to write a service that manages requests for the COM port and then talk to that service from ASP.Net. This will allow for split permissions and controlled single access to the COM port. Any other hack has the potential of causing lots of problems.