VISA Print Server
The VISA Print Server is used to transfer PDF documents via websocket to a VISA Print Client which opens a print dialog on the host computer of the VISA user.
The transfer is triggered by a request from the VISA CUPS Driver when a user prints a document in an instance. It clients are available it will send chunked data to all that have printing enabled.
The VISA Print Client, an angular module integrated into the VISA front end, receives the PDF data and informs the user/opens a print dialog.
An authentication proxy is used to ensure that only the owner of an instance can connect to the VISA Print Server and receive print requests.
The user then selects a local printer to print the document or saves the PDF as a local file.
Building and running
The server can be built and run from source as follows:
npm install
npm start
You can also run it directly from the npm pacakge:
npm i -g @illgrenoble/visa-print-server
visa-print-server
Configuration
The following environment variables can be set to configure the VISA Print Server:
| Environment variable | default value | description |
|---|
| VISA_PRINT_SERVER_HOST | localhost | Host on which the web server listens to |
| VISA_PRINT_SERVER_PORT | 8091 | The web server port |
| VISA_PRINT_SERVER_AUTH_TOKEN | | An authorisation token that (when set) must be added to the request header x-auth-token |
| VISA_PRINT_SERVER_WEBSOCKET_MAX_DATA | 16384 | Maximum chunk size that is sent via the websocket |
The environment variables can be stored in a .env file.
Demo
A demo is available to quickly test the connection between a client and a server, the transfer of a PDF file via websocket and the opening of the print dialog in the client.
To start the server locally run the following commands in a terminal:
npm i -g @illgrenoble/visa-print-server
visa-print-server
This will start up the VISA Print Server on localhost:8091 without authentication enabled.
In another terminal, use the following commands to build and run the client:
git clone https://github.com/ILLGrenoble/visa-print-client.git
cd visa-print-client
npm install
npm run build:lib
npm start
The client will automatically connect to the websocket server on localhost and enable the printing queue. Open a browser window at http://localhost:4200 (you should only see a grey window). In a debug console you should see that the websocket is connected and printing enabled.
To test the transfer of a PDF file, from another terminal perform the following command:
curl -X POST http://localhost:8091/api/printer --data-urlencode "path=<path_to_a_pdf>" --data-urlencode "jobId=1"
Change path_to_a_pdf to the absolute path of a PDF file on your computer. The print dialog should open on the client app with the PDF available for printing.
