**Only one process** in the server can be listening on a specific **port** in a specific **IP address**. There could be other processes listening on other ports in the same IP address, but only one for each combination of IP address and port.

TLS (HTTPS) uses the specific port `443` by default. So that's the port we would need.

      run = true;
    }
  }

  private static class TestCallable implements Callable<String> {
    @Override
    public String call() {
      return "foo";
    }
  }

  /** Simple same thread listening executor service that doesn't handle shutdown. */
  private static class TestListeningExecutorService extends AbstractListeningExecutorService {

    @Override
    public void execute(Runnable runnable) {

      run = true;
    }
  }

  private static class TestCallable implements Callable<String> {
    @Override
    public String call() {
      return "foo";
    }
  }

  /** Simple same thread listening executor service that doesn't handle shutdown. */
  private static class TestListeningExecutorService extends AbstractListeningExecutorService {

    @Override
    public void execute(Runnable runnable) {

        } finally {
            if (tempDocRoot) {
                docRoot.delete();
            }
        }
    }

    /**
     * Get the actual port the server is listening on.
     * This is useful when starting the server with port 0 to get a random available port.
     *
     * @return the actual port number
     */
    public int getPort() {

        } finally {
            if (tempDocRoot) {
                docRoot.delete();
            }
        }
    }

    /**
     * Get the actual port the server is listening on.
     * This is useful when starting the server with port 0 to get a random available port.
     *
     * @return the actual port number
     */
    public int getPort() {

Remember from the docs [About HTTPS](https.md) that only one process can be listening on one combination of port and IP address in a server?

This is still true.

So, to be able to have **multiple processes** at the same time, there has to be a **single process listening on a port** that then transmits the communication to each worker process in some way.

///

## Deployment Concepts { #deployment-concepts }

These examples run the server program (e.g Uvicorn), starting **a single process**, listening on all the IPs (`0.0.0.0`) on a predefined port (e.g. `80`).

This is the basic idea. But you will probably want to take care of some additional things, like:

* Security - HTTPS
* Running on startup
* Restarts

### Load Balancer { #load-balancer }

When using containers, you would normally have some component **listening on the main port**. It could possibly be another container that is also a **TLS Termination Proxy** to handle **HTTPS** or some similar tool.

그런 경우에는 [위에서 설명한 대로](#dockerfile) 의존성을 설치하고, 여러 Uvicorn 워커를 사용하는 대신 **단일 Uvicorn 프로세스**를 실행하는 **처음부터 만든 Docker 이미지**를 사용하는 것이 좋을 것입니다.

### 로드 밸런서 { #load-balancer }

컨테이너를 사용할 때는 보통 **메인 포트에서 대기(listening)하는** 컴포넌트가 있습니다. **HTTPS**를 처리하기 위한 **TLS 종료 프록시** 역할을 하는 다른 컨테이너일 수도 있고, 유사한 도구일 수도 있습니다.

이 컴포넌트가 요청의 **부하(load)**를 받아 워커들에 (가능하면) **균형 있게** 분산한다면, 보통 **로드 밸런서**라고 부릅니다.

/// tip | 팁

- Slow container runtime initialization no longer causes the System WatchDog to kill the kubelet. The Device Manager was treated as unhealthy until it began listening on its port. ([#135153](https://github.com/kubernetes/kubernetes/pull/135153), [@SergeyKanzhelev](https://github.com/SergeyKanzhelev))