# WebSockets

When defining WebSockets, you normally declare a parameter of type `WebSocket` and with it you can read data from the client and send data to it.

It is provided directly by Starlette, but you can import it from `fastapi`:

```python
from fastapi import WebSocket
```

/// tip

eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c
```

It is not encrypted, so, anyone could recover the information from the contents.

But it's signed. So, when you receive a token that you emitted, you can verify that you actually emitted it.

## Install the Server Program { #install-the-server-program }

When you install FastAPI, it comes with a production server, Uvicorn, and you can start it with the `fastapi run` command.

But you can also install an ASGI server manually.

	AssertAssociationCount(t, users, "Account", 2, "")

	// Find
	var accounts []Account
	if DB.Model(&users).Association("Account").Find(&accounts); len(accounts) != 2 {
		t.Errorf("accounts count should be %v, but got %v", 3, len(accounts))
	}

	// Append
	DB.Model(&users).Association("Account").Append(
		&Account{Number: "account-slice-append-1"},
		&Account{Number: "account-slice-append-2"},

   * Attack the CA intermediates check by presenting unrelated chains to the handshake vs.
   * certificate pinner.
   *
   * This chain is valid but not pinned:
   *
   * ```
   *   attackerCa
   *    -> phonyVictim
   * ```
   *
   *
   * This chain is pinned but not valid:
   *
   * ```
   *   attackerCa
   *     -> pinnedRoot (trusted by CertificatePinner)

/**
 * Outer class that exists solely to let us write {@code Partially.GwtIncompatible} instead of plain
 * {@code GwtIncompatible}. This is more accurate for {@link Futures#catching}, which is available
 * under GWT but with a slightly different signature.
 *
 * <p>We can't use {@code PartiallyGwtIncompatible} because then the GWT compiler wouldn't recognize

They tend to require more complex configurations, a message/job queue manager, like RabbitMQ or Redis, but they allow you to run background tasks in multiple processes, and especially, in multiple servers.

            of those modules are ones that it uses but forgets to list in its own <inherits>, we'd
            like to get an error. Currently we do, but if we add the extra <inherits> lines, we
            won't.

            I have one idea for a better approach, but it's painful, and I haven't tested it: We

   *
   * <p>The expected (but not guaranteed) performance of the special implementation differs from
   * {@code getStackTrace} in one main way: The {@code lazyStackTrace} call itself returns quickly
   * by delaying the per-stack-frame work until each element is accessed. Roughly speaking:
   *
   * <ul>
   *   <li>{@code getStackTrace} takes {@code stackSize} time to return but then negligible time to

     * is referenced somewhere for as long as the enum class is loaded. *Maybe in theory* the enum
     * class could be unloaded after the above call to `getEnumConstants` but before we call
     * `get()`, but that is vanishingly unlikely.
     */
    return ref == null ? Optional.absent() : Optional.fromNullable(enumClass.cast(ref.get()));
  }

  static String formatCompact4Digits(double value) {