Cannot make gRPC postman request to nestjs server

Question

I've set up a nestjs server that handles gRPC requests. In order to do some ad-hoc debugging, I'm trying to use postman. However, whenever I try to send a request, postman returns the following error: Received RST_STREAM with code 2 triggered by internal client error: Protocol error.

This is my app.controller.ts file:

import { Metadata, ServerUnaryCall } from '@grpc/grpc-js';
import { Controller } from '@nestjs/common';
import { GrpcMethod } from '@nestjs/microservices';
import { BaseLoggingService } from './common/baseLogging.service';
import { CreateLogRequest, CreateLogResponse } from './generated/logs';

@Controller()
export class AppController {
  constructor(private baseLoggingService: BaseLoggingService) {}

  @GrpcMethod('LogService', 'CreateLog')
  async createLog(
    req: CreateLogRequest,
    metadata: Metadata,
    call: ServerUnaryCall<CreateLogRequest, CreateLogResponse>,
  ): Promise<CreateLogResponse> {
    return await this.baseLoggingService.createLog(req);
  }
}

The interfaces CreateLogRequest and CreateLogResponse are generated by protobuf-ts/plugin, and are based on the following .proto file:

/**
* Definitions of shared interfaces 
**/

syntax = "proto3";

package logs;

enum LogLevel {
  INFO = 0;
  WARN = 1;
  ERROR = 2;
  DEBUG = 3;
}

message LogContext {
  string sessionId = 1;
  string requestId = 2;
  string hostname = 3;
  string podName = 4;
  string grpcMethodName = 5;
  uint32 durationMs = 6;
}

message ErrorData {
  string name = 1;
  string notificationCode = 2;
  string stack = 3;
}

message CreateLogRequest {
  LogLevel level = 1;
  string service = 2;
  int32 timestamp = 3;
  string message = 4;
  LogContext context = 5;
  ErrorData errorData = 6;
}

message CreateLogResponse {
  LogLevel level = 1;
  string service = 2;
  int32 code = 3;
}

service LogService {
  rpc CreateLog (CreateLogRequest) returns (CreateLogResponse) {}
}

The server instance is running on a remote machine, so I am using ssh-tunneling to send the requests. Here is the postman request and response. There is no authentication in place.

I used server logs and the controller's createLog function does not get triggered at all when making the request. I even tried using grpcurl, which fails again, albeit for a differently inexplicable reason:

 grpcurl -plaintext -d '{
    "context": {
        "durationMs": 4100079420,
        "grpcMethodName": "magna ut commodo",
        "hostname": "exercitation dolor",
        "podName": "ad Duis non",
        "requestId": "do",
        "sessionId": "nostrud"
    },
    "errorData": {
        "name": "nostrud enim Lorem consectetur",
        "notificationCode": "in anim",
        "stack": "incididunt"
    },
    "level": 0,
    "message": "eu qui dolore laborum eiusmod",
    "service": "sunt",
    "timestamp": -499959849
}' localhost:6666 LogService/CreateLog
Failed to dial target host "localhost:6666": context deadline exceeded