# emqtt
MQTT client library and command line tools implemented in Erlang that supports MQTT v5.0/3.1.1/3.1.
# Getting started
## As a Command Line Tool
### Build
```
$ make
```
Once you've compiled successfully you will get a script called `emqtt` in `_buile/emqtt/rel/emqtt/bin`. We can see what `emqtt` can do with `--help` option:
```
$ ./emqtt --help
Usage: emqtt pub | sub [--help]
```
`emqtt pub` is used to publish a single message on a topic and exit. `emqtt sub` is used to subscribe to a topic and print the messages that it receives.
### Command-line Syntax
Options can have both short (single character) and long (string) option names.
A short option can have the following syntax:
```
-e arg Single option 'e', argument "arg"
```
A long option can have the following syntax:
```
--example=arg Single option 'example', argument "arg"
--example arg Single option 'example', argument "arg"
```
### Publish
#### Synopsis
```
./emqtt pub [-h [<host>]] [-p <port>] [-I <iface>]
[-V [<protocol_version>]] [-u <username>]
[-P <password>] [-C <clientid>] [-k [<keepalive>]]
[-t <topic>] [-q [<qos>]] [-r [<retain>]]
[--help <help>] [--will-topic <will_topic>]
[--will-payload <will_payload>]
[--will-qos [<will_qos>]]
[--will-retain [<will_retain>]]
[--enable-websocket [<enable_websocket>]]
[--enable-ssl [<enable_ssl>]]
[--tls-version [<tls_version>]]
[--CAfile <cafile>] [--cert <cert>]
[--key <key>] [--payload <payload>]
[--repeat [<repeat>]]
[--repeat-delay [<repeat_delay>]]
```
#### Options
<span id="host">**`-h, --host`**</span>
  Specify the host to connect to, support for domain name and IP address. Defaults to localhost.
<span id="port">**`-p, --port`**</span>
  Specify the port to connect to. If not given, the default of 1883 for MQTT or 8883 for MQTT over TLS will be used.
<span id="iface">**`-I, --iface`**</span>
  Specify the network interface or ip address to use.
<span id="protocol-version">**`-V, --protocol-version`**</span>
  Specify the MQTT protocol version used by the client. Can be `v3.1`, `v3.1.1` and `v5`. Defaults to `v5`.
<span id="username">**`-u, --username`**</span>
  Specify the username that can be used by the broker for authentication and authorization.
<span id="password">**`-P, --password`**</span>
  Specify the password for the username.
<span id="clientid">**`-C, --clientid`**</span>
  Specify the client identifier. If not given, the client identifier in the format `emqtt-<Hostname>-<Random Hexadecimal String>` will be automatically generated by `emqtt_cli`.
<span id="keepalive">**`-k, --keepalive`**</span>
  Specify the interval in seconds sending PINGREQ packets to the broker. Defaults to 300 seconds.
**`-t, --topic`**
  Specify the MQTT topic you want to publish. If the topic beginning with $, you must use single quote(`'`) to specify the topic rather than double quotes(`"`). This is a required option.
**`-q, --qos`**
  Specify the quality of service for the message. Can be 0, 1 and 2. Defaults to 0.
**`-r, --retain`**
  Specify whether the message is a retained message. Defaults to false.
**`--payload`**
  Specify the application message is to be published. This is a required option.
**`--repeat`**
  Specify the number of times the message will be repeatedly published. Defaults to 1.
**`--repeat-count`**
  Specify the number of seconds to wait after the previous message was delivered before publishing the next. Defaults to 0, it means to publish repeated messages as soon as the previous message is sent.
<span id="will-topic">**`--will-topic`**</span>
  Specify the topic of the will message sent when the client disconnects unexpectedly.
<span id="will-qos">**`--will-qos`**</span>
  Specify the quality of service of the will message. Defaults to 0. This must be used in conjunction with `--will-topic`.
<span id="will-retain">**`--will-retain`**</span>
  Specify whether the will message is a retained message. Defaults to false. This must be used in conjunction with `--will-topic`.
<span id="will-payload">**`--will-payload`**</span>
  Specify the application message that will be stored by the broker and sent out if this client disconnects unexpectedly. This must be used in conjunction with `--will-topic`.
<span id="enable-websocket">**`--enable-websocket`**</span>
  Specify enable WebSocket transport or not. This option can't be used with `--enable-ssl` currently.
<span id="enable-ssl">**`--enable-ssl`**</span>
  Specify enable SSL/TLS transport or not. This option can't be used with `--enable-websocket` currently.
<span id="tls-version">**`--tls-version`**</span>
  Specify which TLS protocol version to use when communicating with the broker. Valid options are tlsv1.3, tlsv1.2, tlsv1.1 and tlsv1. Defaults to tlsv1.2.
<span id="CAfile">**`--CAfile`**</span>
  Specify the path to a file containing PEM encoded CA certificates. This must be used in conjunction with `--enable-ssl`.
<span id="cert">**`--cert`**</span>
  Specify the path to a file containing a PEM encoded certificate for this client, if required by the server. This must be used in conjunction with `--enable-ssl`.
<span id="key">**`--key`**</span>
  Specify the path to a file containing a PEM encoded private key for this client, if required by the server. This must be used in conjunction with `--enable-ssl`.
#### Examples
**Publish a simple message over a TCP connection**
```
$ ./emqtt pub -t "hello" --payload "hello world"
Client emqtt-zhouzibodeMacBook-Pro-4623faa14d8256e9cb95 sent CONNECT
Client emqtt-zhouzibodeMacBook-Pro-4623faa14d8256e9cb95 sent PUBLISH (Q0, R0, D0, Topic=hello, Payload=...(11 bytes))
Client emqtt-zhouzibodeMacBook-Pro-4623faa14d8256e9cb95 sent DISCONNECT
```
**Publish a simple message over a TLS connection**
```
$ ./emqtt pub --enable-ssl=true -t "hello" --payload "hello world" --CAfile=certs/cacert.pem --cert=certs/client-cert.pem --key=certs/client-key.pem
Client emqtt-zhouzibodeMacBook-Pro-cec9489c26e3ed7a38eb sent CONNECT
Client emqtt-zhouzibodeMacBook-Pro-cec9489c26e3ed7a38eb sent PUBLISH (Q0, R0, D0, Topic=hello, Payload=...(11 bytes))
Client emqtt-zhouzibodeMacBook-Pro-cec9489c26e3ed7a38eb sent DISCONNECT
```
**Publish a message repeatedly over a WebSocket connection**
```
$ ./emqtt pub --enable-websocket=true -p 8083 -t "hello" --payload "hello world"
Client emqtt-zhouzibodeMacBook-Pro-1e4677ab46cecf1298ac sent CONNECT
Client emqtt-zhouzibodeMacBook-Pro-1e4677ab46cecf1298ac sent PUBLISH (Q0, R0, D0, Topic=hello, Payload=...(11 bytes))
Client emqtt-zhouzibodeMacBook-Pro-1e4677ab46cecf1298ac sent DISCONNECT
```
### Subscribe
#### Synopsis
```
./emqtt sub [-h [<host>]] [-p <port>] [-I <iface>]
[-V [<protocol_version>]] [-u <username>]
[-P <password>] [-C <clientid>] [-k [<keepalive>]]
[-t <topic>] [-q [<qos>]] [--help <help>]
[--will-topic <will_topic>]
[--will-payload <will_payload>]
[--will-qos [<will_qos>]]
[--will-retain [<will_retain>]]
[--enable-websocket [<enable_websocket>]]
[--enable-ssl [<enable_ssl>]]
[--tls-version [<tls_version>]]
[--CAfile <cafile>] [--cert <cert>]
[--key <key>]
[--retain-as-publish [<retain_as_publish>]]
[--retain-handling [<retain_handling>]]
```
#### Options
**`-h, --host`**
  See also [--host](#host).
**`-p, --port`**
  See also [--port](#port).
**`-I, --iface`**
  See also [--iface](#iface).
**`-V, --protocol-version`**
  See also [--protocol-version](#protocol-version).
**`-u, --username`**
  See also [--username](#username).
**`-P, --password`**
  See also [--password](#password).
**`-C, --clientid`**
  See also [--clientid](#clientid).
**`-k, --keepalive`**
  See also [--keepalive](#keepalive).
**`-t, --topic`**
  Specify the MQTT topic you want to subscribe to. This is a required option.
**`-q, --qos`**
  Specify the maximum qos level at which the broker can send application messages to the client. Defaults to 0.
**`--retain-as-publish`**
  Specify the Retain As Publish option in subscription options. Defaults to 0.
**`--retain-handling`**
  Specify the Retain Handling option in subscription options. Defaults to 0.
**`--will-topic`**
  See also [--will-topic](#will-topic).
**`--will-qos`**
  See also [--will-qos](#will-qos).
**`--will-retain`**
  See also [--will-retain](#will-retain).
**`--will-payload`**
  See also [--will-payload](#will-payload).
**`--enable-websocket`**
  See also [--enable-websocket](#enable-websocket).
**`--enable-ssl`**
  See also [--enable-ssl](#enable-ssl).
**`--tls-version`**
  See also [--tls-version](#tls-version).
**`--CAfile`**
  See also [--CAfile](#CAfile).
**`--cert`**
  See also [--cert](#cert).
**`--key`**
  See also [--key](#key).
#### Examples
**Build Non-shared Subscription and Recv "hello world"**
```
$ ./emqtt sub -t "hello"
Client emqtt-zhouzibodeMacBook-Pro-1686fee6fdb99f674f2c sent CONNECT
Client emqtt-zhouzibodeMacBook-Pro-1686fee6fdb99f674f2c subscribed to hello
hello world
```
**Build Shared Subscription and Recv "hello world"**
```
$ ./emqtt sub -t '$share/group/hello'
Client emqtt-zhouzibodeMacBook-Pro-288e65bb3f4013d30249 sent CONNECT
Client emqtt-zhouzibodeMacBook-Pro-288e65bb3f4013d30249 subscribed to $share/group/hello
hello world
```
----
## As a Dependency Library
### Add to rebar3 project
Add to `rebar.config`
```erlang
...
{deps, [{emqtt, {git, "https://github.com/emqx/emqtt", {tag, "v1.2.0"}}}]}.
...
```
### Build
```
$ rebar3 compile
```
### Data Types
<span id="option">**option()**</span>
```
option() = {name, atom()} |
{owner, pid()} |
{host, host()} |
{port, inet:port_number()} |
{tcp_opts, [gen_tcp:option()]} |
{ssl, boolean()} |
{ssl_opts, [ssl:ssl_option()]} |
{ws_path, string()} |
{connect_timeout, pos_integer()} |
{bridge_mode, boolean()} |
{clientid, iodata()} |
{clean_start, boolean()} |
{username, iodata()} |
{password, iodata()} |
{proto_ver, v3 | v4 | v5} |
{keepalive, non_neg_integer()} |
{max_inflight, pos_integer()} |
{retry_interval, pos_integer()} |
{will_topic, iodata()} |
{will_payload, iodate()} |
{will_retain, boolean()} |
{will_qos, qos()} |
{will_props, properties()} |
{auto_ack, boolean()} |
{ack_timeout, pos_integer()} |
{force_ping, boolean()} |
{properties, properties()}
```
<span id="client">**client()**</span>
```
client() = pid() | atom()
```
<span id="host">**host()**</span>
```
host() = inet:ip_address() | inet:hostname()
```
<span id="properties">**properties()**</span>
```
properties() = #{'Payload-Format-Indicator' => 0..1,
'Message-Expiry-Interval' => 0..16#FFFFFFFF,
'Content-Type' => binary(),
'Response-Topic' => binary(),
'Correlation-Data' => binary(),
'Subscription-Identifier' => 0..16#7FFFFFFF,
'Session-Expiry-Interval' => 0..16#FFFFFFFF,
'Assigned-Client-Identifier' => binary(),
'Server-Keep-Alive' => 0..16#FFFF,
'Authentication-Method' => binary(),
'Authentication-Data' => binary(),
'Request-Problem-Information' => 0..1,
'Will-Delay-Interval' => 0..16#FFFFFFFF,
'Request-Response-Information' => 0..1,
'Response-Information' => binary(),
'Server-Reference' => binary(),
'Reason-String' => binary(),
'Receive-Maximum' => 1..16#FFFF,
'Topic-Alias-Maximum' => 0..16#FFFF,
'Topic-Alias' => 1..16#FFFF,
'Maximum-QoS' => 0..1,
'Retain-Available' => 0..1,
'User-Property' => [{binary(), binary()}],
'Maximum-Packet-Size' => 1..16#FFFFFFFF,
'Wildcard-Subscription-Available' => 0..1,
'Subscription-Identifier-Available' => 0..1,
'Shared-Subscription-Available' => 0..1}
```
<span id="qos">**qos()**</span>
```
qos() = 0 | 1 | 2
```
**qos_name()**
```
qos_name() = qos0 | at_most_once |
qos1 | at_least_once |
qos2 | exactly_once
```
<span id="topic">**topic()**</span>
```
topic() = binary()
```
<span id="payload">**payload()**</span>
```
payload() = iodata()
```
<span id="packetid">**packet_id()**</span>
```
packet_id() = 0..16#FFFF
```
<span id="subopt">**subopt()**</span>
```
subopt() = {rh, 0 | 1 | 2} |
{rap, boolean()} |
{nl, boolean()} |
{qos, qos() | qos_name()}
```
<span id="pubopt">**pubopt()**</span>
```
pubopt() = {retain, boolean()} |
{qos, qos() | qos_name()}
```
<span id="reasoncode">**reason_code()**</span>
```
reason_code() = 0..16#FF
```
### Exports
**emqtt:start_link() -> {ok, Pid} | ignore | {error, Reason}**
**emqtt:start_link(Options) -> {ok, Pid} | ignore | {error, Reason}**
  **Types**
    **Pid = pid()**
    **Reason = term()**
    **Options = [[option()](#option)]**
Start MQTT client process with specified options. `Options` will be used in connecting and running.
The following options are available:
`{name, Name}`
If a name is provided, the gen_statem will be registered with this name. For details see the documentation for the first argument of `gen_statem:start_link/4`.
`{owner, Pid}`
Client process will send messages like `{diconnected, ReasonCode, Properties}` to the owner process.
`{host, Host}`
The host of the MQTT server to be connected. Host can be a hostname or an IP address. Defaults to `localhost`
`{port, Port}`
The port of the MQTT server to be connected. If not given, the default of 1883 for MQTT or 8883 for MQTT over TLS will be used.
`{tcp_opts, Options}`
Additional options for `gen_tcp:connect/3`.
`{ssl, boolean()}`
Enable SSL/TLS transport or not. Defaults to false.
`{ssl_opts, Options}`
Additional options for `ssl:connect/3`.
`{ws_path, Path}`
Path to the resource. Defaults to `/mqtt`
`{connect_timeout, Timeout}`
The maximum time to wait to connect to the server and the server returns a CONNACK. Defaults to 60s.
`{bridge_mode, boolean()}`
Enable bridge mode or not. Defaults to false.
`{clientid, ClientID}`
Specify the client identifier. If not given, the client identifier will use the value assigned by the server in MQTT v5 or be automatically generated by internal code in MQTT v3.1/v3.1.1.
`{clean_start, CleanStart}`
Whether the server should discard any existing session and start a new session. Defaults to true.
`{username, Username}`
Username used by the server for authentication and authorization.
`{password, Password}`
Password used by the server for authentication and authorization.
`{proto_ver, ProtocolVersion}`
MQTT protocol version. Defaults to `v4`.
`{keepalive, Keepalive}`
Maximum time interval that is permitted to elapse between the point at which the Client finishes transmitting one MQTT Control Packet and the point it starts sending the next. It will be replaced by server keep alive returned from MQTT server.
`{max_inflight, MaxInflight}`
Max number of QoS 1 and QoS 2 packets in flight. In other words, the number of packets that were sent but not yet acked. Defaults to `infinity`, means no limit.
`{retry_interval, RetryInterval}`
Interval to retry sending packets that have been sent but not received a response. Defaults to 30s.
`{will_topic, WillTopic}`
Topic of will message.
`{will_payload, WillPayload}`
Payload of will message.
`{will_retain, WillRetain}`
Whether the server should publish the will message as a retained message. Defaults to false.
`{will_qos, WillQoS}`
QoS of will message. Defaults to 0.
`{will_props, WillProperties}`
Properties of will message.
`{auto_ack, boolean()}`
If true (the default), cliean process will automatically send ack packet like PUBACK when it receives a packet from the server. If false, application decides what to do.
`{ack_timeout, AckTimeout}`
Maximum time to wait for a reply message. Defaults to 30s.
`{force_ping, boolean()}`
If false (the default), if any other packet is sent during keep alive interval, the ping packet will not be sent this time. If true, the ping packet will be sent every time.
`{properties, Properties}`
Properties of CONNECT packet.
**emqtt:connect(Client) -> {ok, Properties} | {error, Reason}**
  **Types**
    **Client = [client()](#client)**
    **Properties = [properties()](#properties)**
    **Reason = timeout | inet:posix() | any()**
Connect to the MQTT server over TCP or TLS and send a `CONNECT` packet with the options specified in `start_link/1, 2`. `Client` must be a pid returned from `start_link/1, 2` or a name specified in `start_link/1, 2`.
Returns:
- `{ok, Properties}` if a MQTT connection is established. `Properties` is propterties in CONNACK packet returned from MQTT server.
- `{error, timeout}` if connection can't be established within the specified time
- `{error, inet:posix()}` A POSIX error value if something else goes wrong.
**emqtt:ws_connect(Client) -> {ok, Properties} | {error, Reason}**
  **Types**
    Same as `emqtt:connect/1`
Connect to the MQTT server over Websocket and send a `CONNECT` packet with the options specified in `start_link/1, 2`. `Client` must be a pid returned from `start_link/1, 2` or a name specified in `start_link/1, 2`.
**emqtt:disconnect(Client) -> ok | {error, Reason}**
**emqtt:disconnect(Client, ReasonCode) -> ok | {error, Reason}**
**emqtt:disconnect(Client, ReasonCode, Properties) -> ok | {error, Reason}**
  **Types**
    **Client = [client()](#client)**
    **ReasonCode = [reason_code()](#reasoncode)**
    **Properties = [properties()](#properties)**
    **Reason = closed | inet:posix()**
Send a `DISCONNECT` packet to the MQTT server. `ReasonCode` specifies a MQTT reason code for `DISCONNECT` packet, defaults to 0 meaning normal disconnection. `Properties` specifies properties for `DISCONNECT` packet, defaults to `#{}` meaning no properties are attached.
**emqtt:ping(Client) -> pong | {error, Reason}**
  **Types**
    **Client = [client()](#client)**
    **Reason = ack_timeout**
Send a `PINGREQ` packet to the MQTT server. If `PINGRESP` packet is received from the server within the timeout period, `pong` is returned. If not, `{error, ack_timeout}` is returned.
**emqtt:subscribe(Client, Properties, Subscriptions) -> {ok, Properties, ReasonCodes} | {error, Reason})**
  **Types**
    **Client = [client()](#client)**
    **Properties = [properties()](#properties)**
    **Subscriptions = [{[topic()](#topic), [[subopt()](#subopt)]}]**
    **ReasonCodes = [[reason_code()](#reasoncode)]**
    **Reason = term()**
Send a `SUBSCRIBE` packet to the MQTT server. `Properties` specifies properties for `SUBSCRIBE` packet, defaults to `#{}` meaning no properties are attached. `Subscriptions` specifies pairs of topic filter and subscription options. The topic filter is requried, the subscription options can be `[]`, equivalent to `[{rh, 0}, {rap, 0}, {nl, 0}, {qos, 0}]`.
**emqtt:unsubscribe(Client, Properties, Topics) -> {ok, Properties, ReasonCodes} | {error, Reason})**
  **Types**
    **Client = [client()](#client)**
    **Properties = [properties()](#properties)**
    **Topics = [[topic()](#topic)]**
    **ReasonCodes = [[reason_code()](#reasoncode)]**
    **Reason = term()**
Send a `UNSUBSCRIBE` packet to the MQTT server. `Properties` specifies properties for `SUBSCRIBE` packet, defaults to `#{}` meaning no properties are attached. `Topics` specifies a list of topic filter with at least one topic filter.
**emqtt:publish(Client, Topic, Properties, Payload, PubOpts) -> ok | {ok, PacketId} | {error, Reason})**
  **Types**
    **Client = [client()](#client)**
    **Topic = [topic()](#topic)**
    **Properties = [properties()](#properties)**
    **Payload = [payload()](#payload)**
    **PubOpts = [[pubopt()](#pubopt)]**
    **PacketId = [packet_id()](#packetid)**
    **Reason = term()**
Send a `PUBLISH` packet to the MQTT server. `Topic`, `Properties` and `Payload` specify topic, properties and payload for `PUBLISH` packet. `PubOpts` specifies qos and retain flag for `PUBLISH` packet, defaults to `[]`, equivalent to `[{qos, 0}, {retain, false}]`.
Returns:
- `ok` Ii a QoS 0 packet is sent.
- `{ok, PacketId}` if a QoS 1/2 packet is sent, the packet identifier will be returned.
- `{error, Reason}` if something goes wrong.
**emqtt:puback(Client, PacketId) -> ok**
**emqtt:puback(Client, PacketId, ReasonCode) -> ok**
**emqtt:puback(Client, PacketId, ReasonCode, Properties) -> ok**
  **Types**
    **Client = [client()](#client)**
    **PacketId = [packet_id()](#packetid)**
    **ReasonCode = [reason_code()](#reasoncode)**
    **Properties = [properties()](#properties)**
Send a `PUBACK` packet to the MQTT server. `PacketId`, `ReasonCode` and `Properties` specify packet identifier, reason code and properties for `PUBACK` packet.
**emqtt:pubrec(Client, PacketId) -> ok**
**emqtt:pubrec(Client, PacketId, ReasonCode) -> ok**
**emqtt:pubrec(Client, PacketId, ReasonCode, Properties) -> ok**
  **Types**
    Same as `emqtt:puback/2, 3, 4`.
Send a `PUBREC` packet to the MQTT server. `PacketId`, `ReasonCode` and `Properties` specify packet identifier, reason code and properties for `PUBREC` packet.
**emqtt:pubrel(Client, PacketId) -> ok**
**emqtt:pubrel(Client, PacketId, ReasonCode) -> ok**
**emqtt:pubrel(Client, PacketId, ReasonCode, Properties) -> ok**
  **Types**
    Same as `emqtt:puback/2, 3, 4`.
Send a `PUBREL` packet to the MQTT server. `PacketId`, `ReasonCode` and `Properties` specify packet identifier, reason code and properties for `PUBREL` packet.
**emqtt:pubcomp(Client, PacketId) -> ok**
**emqtt:pubcomp(Client, PacketId, ReasonCode) -> ok**
**emqtt:pubcomp(Client, PacketId, ReasonCode, Properties) -> ok**
  **Types**
    Same as `emqtt:puback/2, 3, 4`.
Send a `PUBCOMP` packet to the MQTT server. `PacketId`, `ReasonCode` and `Properties` specify packet identifier, reason code and properties for `PUBCOMP` packet.
**emqtt:subscriptions(Client) -> Subscriptions**
  **Types**
    **Client = [client()](#client)**
    **Subscriptions = [{[topic()](#topic), [[subopt()](#subopt)]}]**
Return all subscriptions.
**emqtt:stop(Client) -> ok**
  **Types**
    **Client = [client()](#client)**
Stop a client process.
**emqtt:pause(Client) -> ok**
  **Types**
    **Client = [client()](#client)**
Pause the client process. The paused client process will ignore all `PUBLISH` packets received and not send `PINGREQ` packet if `force_ping` is set to false.
**emqtt:resume(Client) -> ok**
  **Types**
    **Client = [client()](#client)**
Resume a client process from a paused state.
### Examples
```
{ok, ConnPid} = emqtt:start_link([{clientid, ClientId}]).
{ok, _Props} = emqtt:connect(ConnPid).
SubOpts = [{qos, 1}].
{ok, _Props, _ReasonCodes} = emqtt:subscribe(ConnPid, #{}, [{<<"hello">>, SubOpts}]).
ok = emqtt:publish(ConnPid, <<"hello">>, #{}, <<"Hello World!">>, [{qos, 0}]).
{ok, _PktId} = emqtt:publish(ConnPid, <<"hello">>, #{}, <<"Hello World!">>, [{qos, 1}]).
receive
{disconnect, ReasonCode, Properties} ->
io:format("Recv a DISONNECT packet - ReasonCode: ~p, Properties: ~p~n", [ReasonCode, Properties]);
{publish, PUBLISH} ->
io:format("Recv a PUBLISH packet: ~p~n", [PUBLISH]);
{puback, {PacketId, ReasonCode, Properties}} ->
io:format("Recv a PUBACK packet - PacketId: ~p, ReasonCode: ~p, Properties: ~p~n", [PacketId, ReasonCode, Properties])
end.
{ok, _Props, _ReasonCode} = emqtt:unsubscribe(ConnPid, #{}, <<"hello">]).
ok = emqtt:disconnect(ConnPid).
ok = emqtt:stop(ConnPid).
```
## License
Apache License Version 2.0
## Author
EMQ X Team.
