This is normally called a **webhook**.

## Webhooks steps

The process normally is that **you define** in your code what is the message that you will send, the **body of the request**.

You also define in some way at which **moments** your app will send those requests or events.

This includes, for example:

* Email notifications sent after performing an action:
    * As connecting to an email server and sending an email tends to be "slow" (several seconds), you can return the response right away and send the email notification in the background.
* Processing data:
    * For example, let's say you receive a file that must go through a slow process, you can return a response of "Accepted" (HTTP 202) and process the file in the background.

```Python
app.dependency_overrides = {}
```

/// tip

If you want to override a dependency only during some tests, you can set the override at the beginning of the test (inside the test function) and reset it at the end (at the end of the test function).

	// global Trace system to send HTTP request/response
	// and Storage/OS calls info to registered listeners.
	globalTrace = pubsub.New[madmin.TraceInfo, madmin.TraceType](8)

	// global Listen system to send S3 API events to registered listeners
	globalHTTPListen = pubsub.New[event.Event, pubsub.Mask](0)

	// global console system to send console logs to
	// registered listeners

    opt Tasks
        operation -->> tasks: Send background tasks
    end
    opt Raise other exception
        tasks -->> dep: Raise other exception
    end
    Note over dep: After yield
    opt Handle other exception
        dep -->> dep: Handle exception, can't change response. E.g. close DB session.
    end
```

/// info

							bucket, version.Name, err))
					}
				}

				if !send(result) {
					return
				}
			}

			// All versions resulted in 'ObjectNotFound/VersionNotFound'
			if versionNotFound == len(fivs.Versions) {
				return
			}

			send(healEntryDone(entry.name))

			// Wait and proceed if there are active requests
			waitForLowHTTPReq()
		}

///

## Await for messages and send messages

In your WebSocket route you can `await` for messages and send messages.

```Python hl_lines="48-52"
{!../../docs_src/websockets/tutorial001.py!}
```

You can receive and send binary, text, and JSON data.

## Try it

If your file is named `main.py`, run your application with:

////

//// tab | Python 3.8+

```Python hl_lines="20-21"
{!> ../../docs_src/path_operation_configuration/tutorial003.py!}
```

////

## Description from docstring

//
//	{label:} WORD[.cond] [ arg {, arg} ] (';' | '\n')
//
// It adds any labels to p.pendingLabels and returns the word, cond,
// operand list, and true. If there is an error or EOF, it returns
// ok=false.
//
// line may reuse the memory from scratch.
func (p *Parser) line(scratch [][]lex.Token) (word, cond string, operands [][]lex.Token, ok bool) {
next:
	// Skip newlines.

    opt Tasks
        operation -->> tasks: Send background tasks
    end
    opt Raise other exception
        tasks -->> tasks: Handle exceptions in the background task code
    end
```

/// info | 说明

只会向客户端发送 **一次响应** ，可能是一个错误响应，也可能是来自 *路由函数* 的响应。

在发送了其中一个响应之后，就无法再发送其他响应了。

///

/// tip | 提示