TcpContext

Kind: Class

Source: packages/microservices/ctx-host/tcp.context.ts

Part of: Microservices

TcpContext provides TCP-specific metadata to NestJS microservice message handlers. It exposes the underlying client socket and the pattern associated with the incoming message, allowing handlers to inspect connection details when needed.

Extends: BaseRpcContext

Methods

Diagram

mermaid
graph LR
  Client[TCP Client] --> Server[NestJS TCP Server]
  Server --> Handler[Message Handler]
  Handler --> Context[TcpContext]
  Context --> Socket[getSocketRef()]
  Context --> Pattern[getPattern()]

Usage

ts
import { Controller } from '@nestjs/common';
import { Ctx, MessagePattern, TcpContext } from '@nestjs/microservices';

@Controller()
export class MathController {
  @MessagePattern('sum')
  sum(
    data: number[],
    @Ctx() context: TcpContext,
  ): number {
    const socket = context.getSocketRef();
    const pattern = context.getPattern();

    console.log(`Received "${pattern}" from ${socket.remoteAddress}`);

    return data.reduce((total, value) => total + value, 0);
  }
}

AI Coding Instructions

• Use TcpContext only in handlers invoked through the NestJS TCP microservice transport.
• Inject the context with @Ctx() context: TcpContext alongside @MessagePattern() handlers.
• Use getSocketRef() for connection-level metadata such as remote address or port; avoid mutating or closing the socket unless the transport lifecycle requires it.
• Use getPattern() when logging, tracing, or routing behavior based on the incoming message pattern.

How it works

TcpContext is a public context class for TCP message handling. It extends BaseRpcContext with an argument tuple whose first item is a TcpSocket and whose second item is a string pattern. tcp.context.ts:4-11

• Construct it with [socket, pattern]; its constructor passes that tuple directly to BaseRpcContext. tcp.context.ts:4-12
• getSocketRef() returns the tuple’s first item—the same TcpSocket reference supplied at construction. tcp.context.ts:17-19
• getPattern() returns the tuple’s second item—the supplied pattern string. tcp.context.ts:24-26
• Through BaseRpcContext, it also inherits getArgs() to return the complete tuple and getArgByIndex(index) to return an item at the requested index. base-rpc.context.ts:4-20

ServerTCP.handleMessage() deserializes an incoming message, converts a non-string packet pattern with JSON.stringify, constructs TcpContext from [socket, pattern], and passes that context to either event handling or the matched request handler. server-tcp.ts:93-101 server-tcp.ts:114-120

There is no runtime validation, error throwing, socket I/O, or mutation in TcpContext itself; its constructor stores the supplied tuple via the base class, and its declared methods only read tuple elements. tcp.context.ts:9-26