esc-pos-proxy-capacitor-plugin

A Capacitor 8 plugin for talking to network-attached ESC/POS thermal printers over raw TCP. It can:

• Print — dispatch raw ESC/POS byte sequences to a printer (default port 9100)
• Ping — check whether a printer is reachable and measure round-trip time
• Discover — find printers on the local network via mDNS (_printer._tcp, _pdl-datastream._tcp) plus a subnet scan on common raw-print ports (9100/9101/9102)

Native implementations are provided for Android and iOS. The web implementation is a no-op — browsers can't open raw TCP sockets to a printer.

Install

npm install esc-pos-proxy-capacitor-plugin
npx cap sync

Usage

import { ESCPOSProxy } from 'esc-pos-proxy-capacitor-plugin';

// Raw ESC/POS bytes (init + "Hello" + line feed + cut), base64-encoded
const bytes = new Uint8Array([0x1b, 0x40, 0x48, 0x65, 0x6c, 0x6c, 0x6f, 0x0a, 0x1d, 0x56, 0x00]);
const message = btoa(String.fromCharCode(...bytes));
await ESCPOSProxy.print({ ip: '192.168.1.50', port: 9100, message });

// Check if a printer is reachable
const { online, rtt } = await ESCPOSProxy.ping({ ip: '192.168.1.50', port: 9100 });

// Find printers on the local network
const { printers } = await ESCPOSProxy.discover({ timeout: 10000 });
// → [{ ip: '192.168.1.50', port: 9100, source: 'mdns' | 'scan' }, ...]

API

• print(...)
• ping(...)
• discover(...)
• Interfaces

print(...)

print(options: { message: string; ip: string; port: number; }) => Promise<{ status: string; }>

Send raw ESC/POS bytes to a network printer at the given IP/port.

message must be a base64-encoded string. Callers that already hold a Uint8Array should encode it with btoa(String.fromCharCode(...bytes)) or an equivalent helper before passing it in. Rejects with a descriptive error if the socket fails to connect or write.

| Param | Type | | ------------- | ----------------------------------------------------------- | | options | { message: string; ip: string; port: number; } |

Returns: Promise<{ status: string; }>

ping(...)

ping(options: { ip: string; port?: number; }) => Promise<{ online: boolean; rtt?: number; }>

Check whether a printer is reachable on the given IP/port.

| Param | Type | | ------------- | ------------------------------------------- | | options | { ip: string; port?: number; } |

Returns: Promise<{ online: boolean; rtt?: number; }>

discover(...)

discover(options?: { ports?: number[] | undefined; timeout?: number | undefined; } | undefined) => Promise<{ printers: PrinterDescriptor[]; }>

Discover ESC/POS-ready printers on the local network. Ports default to common raw printing ports (9100/9101/9102). Timeout is the maximum scan duration in milliseconds.

| Param | Type | | ------------- | ---------------------------------------------------- | | options | { ports?: number[]; timeout?: number; } |

Returns: Promise<{ printers: PrinterDescriptor[]; }>

Interfaces

PrinterDescriptor

| Prop | Type | | ------------ | ----------------------------- | | ip | string | | port | number | | source | 'scan' | 'mdns' |