TcpSocket

Kind: Class

Source: packages/microservices/helpers/tcp-socket.ts

TcpSocket wraps a Node.js TCP socket for the microservices transport layer. It manages connection lifecycle events, message transmission, stream data handling, and emission of complete incoming messages after TCP packet framing is processed.

Methods

Method	Signature	Returns
`connect`	`connect(port: number, host: string)`	`void`
`on`	`on(event: string, callback: (err?: any) => void)`	`void`
`once`	`once(event: string, callback: (err?: any) => void)`	`void`
`end`	`end()`	`void`
`sendMessage`	`sendMessage(message: any, callback: (err?: any) => void)`	`void`
`handleSend`	`handleSend(message: any, callback: (err?: any) => void)`	`any`
`handleData`	`handleData(data: Buffer	string)`
`emitMessage`	`emitMessage(data: string)`	`void`

When something fails

TcpSocket handles failure in 2 places: it logs it and continues in 1, and lets it reach the caller in 1.

Diagram

mermaid
graph LR
  Client[ClientTCP / ServerTCP] --> TcpSocket
  TcpSocket -->|connect / end| NetSocket[Node.js net.Socket]
  TcpSocket -->|sendMessage| Outbound[Framed TCP message]
  Outbound --> NetSocket
  NetSocket -->|data| HandleData[handleData]
  HandleData --> EmitMessage[emitMessage]
  EmitMessage --> MessageListeners[message event listeners]

Usage

ts
import { Socket } from 'node:net';
import { TcpSocket } from '@nestjs/microservices/helpers/tcp-socket';

const tcpSocket = new TcpSocket(new Socket());

tcpSocket.on('message', (payload: Buffer) => {
  console.log('Received response:', payload.toString());
});

tcpSocket.once('error', (error: Error) => {
  console.error('TCP connection failed:', error);
});

await tcpSocket.connect(3000, '127.0.0.1');

tcpSocket.sendMessage(
  JSON.stringify({
    pattern: 'health.check',
    data: {},
  }),
);

// Close the connection when no further messages are needed.
tcpSocket.end();

AI Coding Instructions

Use TcpSocket rather than interacting with the underlying net.Socket directly when implementing TCP microservice transport behavior.
Send protocol-compatible serialized messages; TCP is stream-based, so do not assume one data event equals one complete application message.
Register message, error, and close-related listeners before connecting or sending messages to avoid missing early socket events.
Preserve the existing handleData() and emitMessage() flow when changing framing logic, since it is responsible for reconstructing complete messages from streamed chunks.
Call end() during client or server shutdown to release socket resources cleanly.

Methods

When something fails

Diagram

Usage

AI Coding Instructions

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