Barcode Printing with AWS AppStream

Amazon AppStream 2.0 supports local printer redirection, enabling users to print documents, including barcodes, from their streaming applications to printers connected to their local computers.  The below section explores some of the options we have explored for barcode  printing  for ZPL printers

1. Direct ZPL Command Printing:

• When sending ZPL commands from a local laptop using the Zebra JavaScript SDK, the printer successfully receives and prints the output as intended.
• However, when attempting the same from within the AppStream environment, we consistently encounter connection refusals.

• AppStream instances run in a cloud-based, isolated environment, which means that direct access to local printers over HTTP (e.g., 127.0.0.1:9100) is not possible. This is why the connection is successful locally but fails when attempted from AppStream.
• The Zebra SDK works well in a local setting by communicating directly with printers over localhost. However, in AppStream, "localhost" refers to the AppStream server itself, not the client machine, leading to a connection refusal.

2. Image and PDF Printing:

• Store barcodes as images or PDFs and print from AppStream using Print Job Redirection and via local printing.
• Local Computer- Configure Printer preferences, adjustments, label types etc and save these as default preferences.
• In Appstream – Select the local default preferences and print – its prints Successfully.

• Select preferences and click print. With this process, from AppStream, barcode can be printed using barcode settings done in local computer.

      

Possible Solutions Moving Forward

• Option 1 -Print Job Redirection: Leveraging Print Job Redirection for generic print jobs like PDFs or images and print the barcode images/pdfs from Appstream( as above)
• Option 2 -Save barcode images/pdf to a local path mapped to AppStream, allowing users to select and print them manually.
• Option 3 - Save barcode images/pdf to a local path mapped to AppStream. Develop a listener application on the local machine that monitors a specific folder for new barcode files and automatically prints them.
• Option 4 - Utilize a backend service to handle printing tasks (refer earlier post) which communicates with network printers to execute print jobs using ZPL commands. 

Barcode Printing Solution

In the labs, there will be different types of barcode label printers. When designing a solution for barcode systems, it is important to streamline the processes, protocols, and network connectivity to optimize operations and maintenance costs effectively.

1. Network Connectivity 

Transition USB Printers to Ethernet connections (TCP )

Printers that require USB connections and are currently connected to desktops in Zone 3 should gradually transition to Ethernet connections. 

Users can print from different locations with out physically connected printer 

- More secure (firewall protection)

- Queue Management

2. Printer Communications and Protocols

Implement IPP (Internet Printing Protocol) for networked printers, facilitating secure and standardized communication over IP networks. IPP is supported by most modern printers and provides features like encryption and authentication.

Ensure ZPL II-compatible label printers are used  and Print Management Microservice can generate and send ZPL II commands. 

3. Local Network Printing Solutions

To access printers on an  onpremise network

Establish VPN Connection to AWS to the network or via AWS direct Connect

Network Print server – Print server act as intermediary recovering print jobs from print microservice over VPN or Direct Connect and forwarding these jobs to isolated printers

4. Cloud printing Solution

Cloud Printing solution simplifies the architecture, it has direct IP printing/queue management, driver management. 

Reduces the need for on-premise print servers

Authentication, and authorization are integral parts to ensure that only authorized users can execute print jobs, and sensitive documents are handled securely.  Cloud printing provider will provide necessary API keys 

Cloud Printing Solution

With Cloud Printing service, on premise print servers may not be required.  Cloud   printing service typically manages queue management, job distribution and driver management

Options 

If Cloud  Services has to send print jobs directly to Printer behind firewall, then we need to open port 632 to allow incoming IPP traffic to onpremise printers and  VPN connection between cloud service abd Onpremise network 

Printers can be configured to make outbound connection to cloud provider over the network. In such case we just need to configure only the outbound rules

Local Network Printing Solution

API Gateway: Acts as the entry point for job submissions from the eLIMS UI.

Print Microservice: Processes the print jobs and interacts with SNS and SQS for messaging and queue management.

SNS/SQS Queue: Holds print jobs sent by the microservice. It manages the delivery of these jobs to the print servers in a scalable and fault-tolerant manner.

Local and Isolated Print Servers: Push print jobs from the SQS Queue and manage the actual printing process on their respective printers.

UI Printing

If there is no connectivity issues with the printers from the UI, then UI printing can also be used