Transports

Transports (CrossEscPos.Transports)

Desktop transports that feed an ESC/POS stream into a ReceiptPrinter the way a real device receives it — over TCP/IP, a serial port, or USB. They also implement IPrinterResponder, so the printer's status replies (DLE EOT, GS r, Automatic Status Back) are sent back over the same channel.

Desktop only. These use raw sockets, System.IO.Ports and libusb, which don't exist in the browser sandbox — a WASM host feeds ESC/POS in-page instead and doesn't reference this package.

flowchart LR
    host["POS app / client"] -->|ESC/POS bytes| t["NetServer / SerialServer"]
    t -->|FeedEscPos| printer["ReceiptPrinter"]
    printer -.->|status bytes via IPrinterResponder| t
    t -.-> host

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TCP/IP server

Listens for connections and feeds whatever bytes arrive — how most modern POS software talks to a network receipt printer (port 9100 by convention).

using System.Net;
using CrossEscPos.Transports;

var tcp = new NetServer(printer);
tcp.Start(IPAddress.Any, 9100);
// … tcp.IsRunning, tcp.EndPoint …
tcp.Stop();

Serial server

Reads ESC/POS from an RS-232 / virtual serial port.

var serial = new SerialServer(printer);
serial.Start("/dev/ttyUSB0", baudRate: 9600);   // or "COM3" on Windows
// … serial.IsRunning, serial.PortName, serial.BaudRate …
serial.Stop();

To test serial without hardware, create a virtual serial bridge (a linked pair of ports) and point the server at one end and your client at the other — see the repository README's "Testing serial without hardware".

USB

UsbPrinter is a USB client (libusb) used to drive a real or emulated printer over a bulk endpoint. It needs the native libusb-1.0 at runtime (brew install libusb, apt install libusb-1.0-0; bundled on Windows).

Lifetime & threading

Start transports after constructing the printer and stop them on shutdown. Receive happens on a background thread, so if you bind printer state to a UI, set printer.UiDispatch (see Core Emulator → Threading).

tcp.Stop();
serial.Stop();

Browser transports (roadmap)

The desktop transports have browser equivalents on the roadmap — Web Serial and WebUSB behind the same IPrinterResponder seam — so the core logic stays identical. The Blazor Web App already renders pasted/uploaded ESC/POS today; live browser transports are the next step.