### TLS with SNI Extension { #tls-with-sni-extension }

**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.

    int countToRemove = 30;
    AtomicInteger current = new AtomicInteger(countToRemove);

    when(backingMap.get(KEY)).thenReturn(current);
    // it's ok if removal fails: another thread may have done the remove
    when(backingMap.remove(KEY, current)).thenReturn(false);

    assertEquals(countToRemove, multiset.remove(KEY, countToRemove));
    assertEquals(0, current.get());
  }

			isConnected := o.checkConnectivity(o.shutdownCtx)
			if isConnected {
				o.serviceMetrics.setConnSuccess(now)
			} else {
				o.serviceMetrics.setConnFailure(now)
			}
		case <-o.shutdownCtx.Done():
			return
		}
	}
}

// Metrics contains metrics about the authentication plugin service.
type Metrics struct {
	LastReachableSecs, LastUnreachableSecs float64

	// Last whole minute stats

print(f"Hello {name} from Python")
```

/// tip

第二个参数是 <a href="https://docs.python.org/zh-cn/3.8/library/os.html#os.getenv" class="external-link" target="_blank">`os.getenv()`</a> 的默认返回值。

如果没有提供，默认值为 `None`，这里我们提供 `"World"` 作为默认值。

///

然后你可以调用这个 Python 程序：

//// tab | Linux, macOS, Windows Bash

<div class="termy">

```console
// 这里我们还没有设置环境变量
$ python main.py

// 因为我们没有设置环境变量，所以我们得到的是默认值

			return Config{}, err
		}
	} else {
		cfg.RRS.Parity = defaultRRSParity
		if setDriveCount == 1 {
			cfg.RRS.Parity = 0
		}
	}

	// Validation is done after parsing both the storage classes. This is needed because we need one
	// storage class value to deduce the correct value of the other storage class.
	if err = validateParity(cfg.Standard.Parity, cfg.RRS.Parity, setDriveCount); err != nil {
		return Config{}, err

	var wg sync.WaitGroup
	for i := 0; i < count; i++ {
		wg.Add(1)
		go func(user User, language Language) {
			err := db.Model(&user).Association("Languages").Append(&language)
			AssertEqual(t, err, nil)

			wg.Done()
		}(user, languages[i])
	}
	wg.Wait()

	var find User
	err = db.Preload(clause.Associations).Where("id = ?", user.ID).First(&find).Error
	AssertEqual(t, err, nil)

	lc := lru.NewLRU[string, string](0, nil, 0)
	wg := sync.WaitGroup{}
	wg.Add(1000)
	for i := 0; i < 1000; i++ {
		go func(i int) {
			lc.Add(fmt.Sprintf("key-%d", i/10), fmt.Sprintf("val-%d", i/10))
			wg.Done()
		}(i)
	}
	wg.Wait()
	if lc.Len() != 100 {
		t.Fatalf("length differs from expected")
	}
}

func TestLRUInvalidateAndEvict(t *testing.T) {
	var evicted int

	if pb != nil && len(*pb) == p.size {
		p.p.Put(pb)
	}
}

// WriteOnCloser implements io.WriteCloser and always
// executes at least one write operation if it is closed.
//
// This can be useful within the context of HTTP. At least
// one write operation must happen to send the HTTP headers
// to the peer.
type WriteOnCloser struct {
	io.Writer
	hasWritten bool
}

    code][https_server_sample].

 *  **OkHttp now supports prior knowledge cleartext HTTP/2.** Enable this by setting
    `Protocol.H2_PRIOR_KNOWLEDGE` as the lone protocol on an `OkHttpClient.Builder`. This mode
    only supports `http:` URLs and is best suited in closed environments where HTTPS is
    inappropriate.

It is designed to have functions that receive two parameters, one "request" and one "response". Then you "read" parts from the request, and "write" parts to the response. Because of this design, it is not possible to declare request parameters and bodies with standard Python type hints as function parameters.