### Create an Engine

A SQLModel `engine` (underneath it's actually a SQLAlchemy `engine`) is what **holds the connections** to the database.

You would have **one single `engine` object** for all your code to connect to the same database.

{* ../../docs_src/sql_databases/tutorial001_an_py310.py ln[14:18] hl[14:15,17:18] *}

    protected FesenClient getClient() {
        if (!fesenClient.connected()) {
            synchronized (fesenClient) {
                if (!fesenClient.connected()) {
                    fesenClient.connect();
                }
            }
        }
        return fesenClient;
    }

    protected void createMapping(final String mappingName) {
        boolean exists = false;
        try {

<mxfile host="65bd71144e">
    <diagram id="jyERGzDynktFHFRGN0ph" name="Page-1">
        <mxGraphModel dx="3321" dy="2867" grid="1" gridSize="10" guides="1" tooltips="1" connect="1" arrows="1" fold="1" page="1" pageScale="1" pageWidth="1920" pageHeight="1200" math="0" shadow="0">
            <root>
                <mxCell id="0"/>
                <mxCell id="1" parent="0"/>

                format: int32
                maximum: 4294967295
                minimum: 0
                type: integer
              nodeSelectors:
                description: Only connect to this peer on nodes that match one of
                  these selectors.
                items:
                  properties:
                    matchExpressions:
                      items:

#### DNS SRV Records

Many Active Directory and other LDAP services are setup with [DNS SRV Records](https://ldap.com/dns-srv-records-for-ldap/) for high-availability of the directory service. To use this to find LDAP servers to connect to, an LDAP client makes a DNS SRV record request to the DNS service on a domain that looks like `_service._proto.example.com`. For LDAP the `proto` value is always `tcp`, and `service` is usually `ldap` or `ldaps`.

        request,
        clientListener,
        random,
        client.pingIntervalMillis.toLong(),
        null,
        0L,
        client.webSocketCloseTimeout.toLong(),
      )
    webSocket.connect(client)
    return webSocket
  }

  private fun closeWebSockets(
    client: WebSocket,
    server: WebSocket,
  ) {
    server.close(1001, "")
    clientListener.assertClosing(1001, "")

                 },
                 "route": {
                  "cluster": "main_internal",
                  "upgrade_configs": [
                   {
                    "upgrade_type": "CONNECT",
                    "connect_config": {}
                   }
                  ]
                 },
                 "typed_per_filter_config": {
                  "connect_authority": {

<mxfile host="65bd71144e">
    <diagram id="jyERGzDynktFHFRGN0ph" name="Page-1">
        <mxGraphModel dx="3321" dy="2867" grid="1" gridSize="10" guides="1" tooltips="1" connect="1" arrows="1" fold="1" page="1" pageScale="1" pageWidth="1920" pageHeight="1200" math="0" shadow="0">
            <root>
                <mxCell id="0"/>
                <mxCell id="1" parent="0"/>

 * to create an NbtAddress internal to this netbios package), no query is
 * sent on the wire and the only state this object has is it's IP address
 * (but that's enough to connect to a host using *SMBSERVER for CallingName).
 * 
 * 2) IP Address, NetBIOS name, nodeType, groupName - If however a
 * legal NetBIOS name string is used a name query request will retreive

    two addresses are encoded differently, such as `192.168.1.1` and `0::0:0:FFFF:C0A8:101`. Note
    that OkHttp incorrectly rejected valid certificates resulting in a failure to connect; at no
    point were invalid certificates accepted.
 *  New: `OkHttpClient.Builder.minWebSocketMessageToCompress()` configures a threshold for