# Message Channel (/zh-CN/realtime-media/rtm/build/channels-and-topics/message-channel)

> For AI agents: see the complete documentation index at [llms.txt](/llms.txt).

**Message** 频道是 RTM 提供的一种基于 Pub/Sub 模型的频道类型。在 Message 频道中，你需要订阅频道才能接收消息，但你在发布消息时无需额外的加入频道操作。RTM 允许你的 App 中同时存在成千上万个 Message 频道，但由于端侧性能和带宽的限制，单个客户端同时只能订阅有限数量的频道，详见 [API 使用限制](/zh-CN/realtime-media/rtm/reference/usage-limits-and-errors/api-limits)。

<_PlatformTabsGroup>
<_PlatformProcessedMarker groupMode="structured" canonicalPlatform="web" platform="android" />
:::info[信息]
如需接收并处理接收到的消息和事件通知，除了要订阅该频道外，你还需要完成[事件监听](/zh-CN/api-reference/rtm/android/configuration#事件监听)程序的配置。
:::
<_PlatformProcessedMarker close="true" />

<_PlatformProcessedMarker groupMode="structured" canonicalPlatform="web" platform="ios" />
:::info[信息]
如需接收并处理接收到的消息和事件通知，除了要订阅该频道外，你还需要完成[事件监听](/zh-CN/api-reference/rtm/ios/configuration#事件监听)程序的配置。
:::
<_PlatformProcessedMarker close="true" />

<_PlatformProcessedMarker groupMode="structured" canonicalPlatform="web" platform="web" />
:::info[信息]
如需接收并处理接收到的消息和事件通知，除了要订阅该频道外，你还需要完成[事件监听](/zh-CN/api-reference/rtm/web/configuration#事件监听)程序的配置。
:::
<_PlatformProcessedMarker close="true" />

<_PlatformProcessedMarker groupMode="structured" canonicalPlatform="web" platform="harmonyos" />
:::info[信息]
如需接收并处理接收到的消息和事件通知，除了要订阅该频道外，你还需要完成[事件监听](/zh-CN/api-reference/rtm/harmonyos/configuration#事件监听)程序的配置。
:::
<_PlatformProcessedMarker close="true" />

<_PlatformProcessedMarker groupMode="structured" canonicalPlatform="web" platform="unity" />
:::info[信息]
如需接收并处理接收到的消息和事件通知，除了要订阅该频道外，你还需要完成[事件监听](/zh-CN/api-reference/rtm/unity/configuration#事件监听)程序的配置。
:::
<_PlatformProcessedMarker close="true" />

<_PlatformProcessedMarker groupMode="structured" canonicalPlatform="web" platform="flutter" />
:::info[信息]
如需接收并处理接收到的消息和事件通知，除了要订阅该频道外，你还需要完成[事件监听](/zh-CN/api-reference/rtm/flutter/configuration#事件监听)程序的配置。
:::
<_PlatformProcessedMarker close="true" />

<_PlatformProcessedMarker groupMode="structured" canonicalPlatform="web" platform="cpp" />
:::info[信息]
如需接收并处理接收到的消息和事件通知，除了要订阅该频道外，你还需要完成[事件监听](/zh-CN/api-reference/rtm/cpp/configuration#事件监听)程序的配置。
:::
<_PlatformProcessedMarker close="true" />

<_PlatformProcessedMarker groupMode="structured" canonicalPlatform="web" platform="swift" />
:::info[信息]
如需接收并处理接收到的消息和事件通知，除了要订阅该频道外，你还需要完成[事件监听](/zh-CN/api-reference/rtm/swift/configuration#事件监听)程序的配置。
:::
<_PlatformProcessedMarker close="true" />

<_PlatformProcessedMarker groupMode="structured" canonicalPlatform="web" platform="mini-program" />
:::info[信息]
如需接收并处理接收到的消息和事件通知，除了要订阅该频道外，你还需要完成[事件监听](/zh-CN/api-reference/rtm/web/configuration#事件监听)程序的配置。
:::
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</_PlatformTabsGroup>

## 业务类型 [#业务类型]

业务类型是指频道中消息发送者和接收者之间的数据流向关系，而基于 Pub/Sub 模式的消息分发机制可以为配置不同的业务类型提供便利。利用 Message 频道你可以轻松地实现以下几种常用的业务类型：

- **一对一频道**：频道中只有两个用户之间相互通信，你可以使用该业务类型来构建私聊频道。常见的业务场景有一对一私聊、一对一客服支持等。

- **群组频道**：多对多的群组频道，频道中的用户群组可见。例如：工作群、家庭群等。你可以允许所有人加入频道，也可以只允许部分被邀请的人加入频道。常见的业务场景有群聊、社区聊天等。

- **广播频道**：一对多的群组频道，频道中的用户群组可见，但只允许一个人发送消息，其他用户都只能接收消息。常见的业务场景有群公告、群问卷调查等。

- **单播频道**：多对一的群组频道，允许多个用户发送消息，但只有一个用户可以接收消息，常见的业务场景有问卷调查的反馈、IoT 传感器数据上传等需要多端数据聚合的场景。

你可以结合实际场景的需要，在实现业务逻辑时选择其中的一种或多种类型。

## 订阅频道 [#订阅频道]

<_PlatformTabsGroup>
<_PlatformProcessedMarker groupMode="structured" canonicalPlatform="web" platform="android" />
监听了 `onMessageEvent` 事件通知后，你就可以调用 `subscribe` 方法订阅频道，从而接收频道中的消息和事件通知。

```java
String channelName = "test_channel";
SubscribeOptions options = new SubscribeOptions();
options.setWithMessage(true);
options.setWithPresence(true);
options.setWithMetadata(true);
options.setWithLock(true);
mRtmClient.subscribe(channelName, options, new ResultCallback<Void>() {
    @Override
    public void onSuccess(Void responseInfo) {
        log(CALLBACK, "subscribe channel " + channelName + " success");
    }

    @Override
    public void onFailure(ErrorInfo errorInfo) {
        log(ERROR, errorInfo.toString());
    }
});
```

默认情况下，你会收到你所订阅的所有频道的消息事件。如果你无需接收某些特定频道的消息，但仍需接收这些频道中其他类型的事件通知或其他频道的消息，你可以将 `SubscribeOptions` 参数中的 `withMessage` 字段设置为 `false`。

```java
String channelName = "test_channel";
SubscribeOptions options = new SubscribeOptions();
options.setWithMessage(false);
options.setWithPresence(true);
options.setWithMetadata(true);
options.setWithLock(true);
mRtmClient.subscribe(channelName, options, new ResultCallback<Void>() {
    @Override
    public void onSuccess(Void responseInfo) {
        log(CALLBACK, "subscribe channel " + channelName + " success");
    }

    @Override
    public void onFailure(ErrorInfo errorInfo) {
        log(ERROR, errorInfo.toString());
    }
});
```

`subscribe` 方法只允许你一次订阅一个频道。如需订阅多个频道，你可以多次调用该方法。例如，当你想同时订阅频道 `chats.room1` 和频道 `chats.room2` 时，你可以参考如下示例代码：

```java
String channelName1 = "chats.room1";
String channelName2 = "chats.room2";
SubscribeOptions options = new SubscribeOptions();
options.setWithMessage(true);
options.setWithPresence(true);
options.setWithMetadata(true);
options.setWithLock(true);

mRtmClient.subscribe(channelName1, options, new ResultCallback<Void>() {
    @Override
    public void onSuccess(Void responseInfo) {
        log(CALLBACK, "subscribe channel " + channelName1 + " success");
    }

    @Override
    public void onFailure(ErrorInfo errorInfo) {
        log(ERROR, errorInfo.toString());
    }
});

mRtmClient.subscribe(channelName2, options, new ResultCallback<Void>() {
    @Override
    public void onSuccess(Void responseInfo) {
        log(CALLBACK, "subscribe channel " + channelName2 + " success");
    }

    @Override
    public void onFailure(ErrorInfo errorInfo) {
        log(ERROR, errorInfo.toString());
    }
});
```
<_PlatformProcessedMarker close="true" />

<_PlatformProcessedMarker groupMode="structured" canonicalPlatform="web" platform="ios" />
监听了 `didReceiveMessageEvent` 事件通知后，你就可以调用 `subscribeWithChannel` 方法订阅频道，从而接收频道中的消息和事件通知。

```objc
[rtm subscribeWithChannel:@"you_channel" option:nil completion:^(AgoraRtmCommonResponse * _Nullable response, AgoraRtmErrorInfo * _Nullable errorInfo) {
    if (errorInfo == nil) {
        NSLog(@"subscribe success!!");
    } else {
        NSLog(@"subscribe failed, errorCode %d, reason %@", errorInfo.errorCode, errorInfo.reason);
    }
}];
```

默认情况下，你会收到你所订阅的所有频道的消息事件。如果你无需接收某些特定频道的消息，但仍需接收这些频道中其他类型的事件通知或其他频道的消息，请勿将 `AgoraRtmSubscribeOptions` 参数中的 `features` 字段设为 `AgoraRtmSubscribeChannelFeatureMetadata`。

```objc
AgoraRtmSubscribeOptions* opt = [[AgoraRtmSubscribeOptions alloc] init];
opt.features = AgoraRtmSubscribeChannelFeaturePresence;
[rtm subscribeWithChannel:@"you_channel" option:opt completion:^(AgoraRtmCommonResponse * _Nullable response, AgoraRtmErrorInfo * _Nullable errorInfo) {
    if (errorInfo == nil) {
        NSLog(@"subscribe success!!");
    } else {
        NSLog(@"subscribe failed, errorCode %d, reason %@", errorInfo.errorCode, errorInfo.reason);
    }
}];
```

`subscribeWithChannel` 方法只允许你一次订阅一个频道。如需订阅多个频道，你可以多次调用该方法。例如，当你想同时订阅频道 `chats.room1` 和频道 `chats.room2` 时，你可以参考如下示例代码：

```objc
[rtm subscribeWithChannel:@"chats.room1" option:nil completion:^(AgoraRtmCommonResponse * _Nullable response, AgoraRtmErrorInfo * _Nullable errorInfo) {
    if (errorInfo == nil) {
        NSLog(@"subscribe success!!");
    } else {
        NSLog(@"subscribe failed, errorCode %d, reason %@", errorInfo.errorCode, errorInfo.reason);
    }
}];

[rtm subscribeWithChannel:@"chats.room2" option:nil completion:^(AgoraRtmCommonResponse * _Nullable response, AgoraRtmErrorInfo * _Nullable errorInfo) {
    if (errorInfo == nil) {
        NSLog(@"subscribe success!!");
    } else {
        NSLog(@"subscribe failed, errorCode %d, reason %@", errorInfo.errorCode, errorInfo.reason);
    }
}];
```
<_PlatformProcessedMarker close="true" />

<_PlatformProcessedMarker groupMode="structured" canonicalPlatform="web" platform="web" />
监听了 `message` 事件通知后，你就可以调用 `subscribe` 方法订阅频道，从而接收频道中的消息和事件通知。

```javascript
const options = {
    withMessage: true,
    withPresence: true,
    beQuiet : false,
    withMetadata: true,
    withLock: true,
};
const channelName = "test_channel";
try {
    const subscribeResult = await rtmClient.subscribe(channelName, options);
} catch (status) {
    const { operation, reason, errorCode } = status;
    console.log(`${operation} failed, the error code is ${errorCode}, due to: ${reason}.`);
}
```

从 v2.3.0 起，当连接状态为 `CONNECTING`、`DISCONNECTED` 或 `SUSPENDED` 时，你仍可以调用 `subscribe`。SDK 会缓存订阅请求，并在连接恢复后继续执行。

`subscribe` 返回成功表示消息频道订阅已完成，但 Presence 加入可能仍在异步执行。如果需要紧接着调用 Presence API，仍需处理服务尚未就绪或请求失败的异步结果。

如果在订阅完成前对同一频道调用 `unsubscribe`，`subscribe` 请求会返回 `RTM_ERROR_CHANNEL_SUBSCRIBE_CANCELED` (-11040)，随后 SDK 完成取消订阅。取消后到达的迟到消息不会再透传给应用。

默认情况下，你会收到你所订阅的所有频道的消息事件。如果你无需接收某些特定频道的消息，但仍需接收这些频道中其他类型的事件通知或其他频道的消息，你可以将 `SubscribeOptions` 参数中的 `withMessage` 字段设置为 `false`。

```javascript
const options = {
    withMessage: false,
    withPresence: true,
    withMetadata: true,
    withLock: true,
};
const channelName = "test_channel";
try {
    const subscribeResult = await rtmClient.subscribe(channelName, options);
} catch (status) {
    const { operation, reason, errorCode } = status;
    console.log(`${operation} failed, ErrorCode: ${errorCode}, due to: ${reason}.`);
}
```

`subscribe` 方法只允许你一次订阅一个频道。如需订阅多个频道，你可以多次调用该方法。例如，当你想同时订阅频道 `chats.room1` 和频道 `chats.room2` 时，你可以参考如下示例代码：

```javascript
const options = {
    withMessage: true,
    withPresence: true,
    beQuiet : false,
    withMetadata: true,
    withLock: true,
};
const channelName1 = "chats.room1";
const channelName2 = "chats.room2";

try {
    const result1 = await rtmClient.subscribe(channelName1, options);
    // your code
} catch (status) {
    const { operation, reason, errorCode } = status;
    console.log(`${operation} failed, the error code is ${errorCode}, due to: ${reason}.`);
}

try {
    const result2 = await rtmClient.subscribe(channelName2, options);
    // your code
} catch (status) {
    const { operation, reason, errorCode } = status;
    console.log(`${operation} failed, the error code is ${errorCode}, due to: ${reason}.`);
}
```
<_PlatformProcessedMarker close="true" />

<_PlatformProcessedMarker groupMode="structured" canonicalPlatform="web" platform="harmonyos" />
监听了 `message` 事件通知后，你就可以调用 `subscribe` 方法订阅频道，从而接收频道中的消息和事件通知。

```typescript
import { SubscribeOptions } from '@shengwang/rtm-full';
import { RtmError } from '@shengwang/rtm-full';

const channelName = "chat_room";
const options: SubscribeOptions = {
  withMessage: true,
  withPresence: true,
  withMetadata: false,
  withLock: false
};

try {
  const response = await rtmClient.subscribe(channelName, options);
  console.log("Subscribe channel success:", response);
} catch (error) {
  console.error("Subscribe failed:", error);
  if (error instanceof RtmError) {
    console.error(`Subscribe failed: ${error.reason} (code: ${error.errorCode})`);
  }
}
```

默认情况下，你会收到你所订阅的所有频道的消息事件。如果你无需接收某些特定频道的消息，但仍需接收这些频道中其他类型的事件通知或其他频道的消息，你可以将 `SubscribeOptions` 参数中的 `withMessage` 字段设置为 `false`。

```typescript
import { SubscribeOptions } from '@shengwang/rtm-full';
import { RtmError } from '@shengwang/rtm-full';

const channelName = "test_channel";
const options: SubscribeOptions = {
  withMessage: false,
  withPresence: true,
  withMetadata: false,
  withLock:false
};

try {
  const response = await rtmClient.subscribe(channelName, options);
  console.log("Subscribe channel success:", response);
} catch (error) {
  console.error("Subscribe failed:", error);
  if (error instanceof RtmError) {
    console.error(`Subscribe failed: ${error.reason} (code: ${error.errorCode})`);
  }
}
```

`subscribe` 方法只允许你一次订阅一个频道。如需订阅多个频道，你可以多次调用该方法。例如，当你想同时订阅频道 `chats.room1` 和频道 `chats.room2` 时，你可以参考如下示例代码：

```typescript
import { SubscribeOptions } from '@shengwang/rtm-full';
import { RtmError } from '@shengwang/rtm-full';

const channelName1 = "chats.room1";
const channelName2 = "chats.room2";
const options: SubscribeOptions = {
  withMessage: true,
  withPresence: true,
  withMetadata: false,
  withLock: false
};

try {
  const response1 = await rtmClient.subscribe(channelName1, options);
  console.log("Subscribe channel1 success:", response1);
} catch (error) {
  console.error("Subscribe channel1 failed:", error);
  if (error instanceof RtmError) {
    console.error(`Subscribe failed: ${error.reason} (code: ${error.errorCode})`);
  }
}

try {
  const response2 = await rtmClient.subscribe(channelName2, options);
  console.log("Subscribe channel2 success:", response2);
} catch (error) {
  console.error("Subscribe channel2 failed:", error);
  if (error instanceof RtmError) {
    console.error(`Subscribe failed: ${error.reason} (code: ${error.errorCode})`);
  }
}
```
<_PlatformProcessedMarker close="true" />

<_PlatformProcessedMarker groupMode="structured" canonicalPlatform="web" platform="unity" />
监听了 `OnMessageEvent` 事件通知后，你就可以调用 `SubscribeAsync` 方法订阅频道，从而接收频道中的消息和事件通知。

```csharp
var options = new SubscribeOptions();

var (status,response) = await rtmClient.SubscribeAsync("Chat_room", options);
if (status.Error)
{
    Debug.Log(string.Format("{0} is failed, ErrorCode: {1}, due to: {2}", status.Operation, status.ErrorCode, status.Reason));
}
else
{
    Debug.Log(string.Format("Subscribe channel success! at Channel:{0}", response.ChannelName));
}
```

默认情况下，你会收到你所订阅的所有频道的消息事件。如果你无需接收某些特定频道的消息，但仍需接收这些频道中其他类型的事件通知或其他频道的消息，你可以将 `SubscribeOptions` 参数中的 `withMessage` 字段设置为 `false`。

```csharp
var options = new SubscribeOptions();
options.withMessage = fasle;

var (status,response) = await rtmClient.SubscribeAsync("Chat_room", options);
```

`SubscribeAsync` 方法只允许你一次订阅一个频道。如需订阅多个频道，你可以多次调用该方法。例如，当你想同时订阅频道 `chats.room1` 和频道 `chats.room2` 时，你可以参考如下示例代码：

```csharp
var options = new SubscribeOptions();

var (status1,response1) = await rtmClient.SubscribeAsync("chats.room1", options);
if (status1.Error)
{
    // your code
}

var (status2,response2) = await rtmClient.SubscribeAsync("chats.room2", options);
if (status2.Error)
{
    // your code
}
```
<_PlatformProcessedMarker close="true" />

<_PlatformProcessedMarker groupMode="structured" canonicalPlatform="web" platform="flutter" />
监听了 `message` 事件通知后，你就可以调用 `subscribe` 方法订阅频道，从而接收频道中的消息和事件通知。

```dart
final channel = 'chat_room';
try {
    var (status, response) = await rtmClient.subscribe(
        channel,
        withMessage: true,
        withPresence: true,
        withMetadata: true,
        withLock: true,
        beQuite: false);

    if (status.error == true ){
       print('${status.operation} failed, errorCode: ${status.errorCode}, due to ${status.reason}');
    } else {
        print('${status.operation} success!');
    }
} catch (e) {
    print('something went wrong: $e');
}
```

默认情况下，你会收到你所订阅的所有频道的消息事件。如果你无需接收某些特定频道的消息，但仍需接收这些频道中其他类型的事件通知或其他频道的消息，你可以将 `withMessage` 字段设置为 `false`。

```dart
final channel = 'chat_room';
try {
    var (status, response) = await rtmClient.subscribe(
        channel,
        withMessage: false,
        withPresence: true,
        withMetadata: true,
        withLock: true,
        beQuite: false);

    if (status.error == true ){
       print('${status.operation} failed, errorCode: ${status.errorCode}, due to ${status.reason}');
    } else {
        print('${status.operation} success!');
    }
} catch (e) {
    print('something went wrong: $e');
}
```

`subscribe` 方法只允许你一次订阅一个频道。如需订阅多个频道，你可以多次调用该方法。例如，当你想同时订阅频道 `chats.room1` 和频道 `chats.room2` 时，你可以参考如下示例代码：

```dart
final channel1 = 'chats.room1';
final channel2 = 'chats.room2'
try {
    var (status, response) = await rtmClient.subscribe(
        channel1,
        withMessage: false,
        withPresence: true,
        withMetadata: true,
        withLock: true,
        beQuite: false);

    if (status.error == true ){
       print('${status.operation} failed, errorCode: ${status.errorCode}, due to ${status.reason}');
    } else {
        print('${status.operation} success!');
    }
} catch (e) {
    print('something went wrong: $e');
}

try {
    var (status, response) = await rtmClient.subscribe(
        channel2,
        withMessage: false,
        withPresence: true,
        withMetadata: true,
        withLock: true,
        beQuite: false);

    if (status.error == true ){
       print('${status.operation} failed, errorCode: ${status.errorCode}, due to ${status.reason}');
    } else {
        print('${status.operation} success!');
    }
} catch (e) {
    print('something went wrong: $e');
}
```
<_PlatformProcessedMarker close="true" />

<_PlatformProcessedMarker groupMode="structured" canonicalPlatform="web" platform="cpp" />
监听了 `onMessageEvent` 事件通知后，你就可以调用 `subscribe` 方法订阅频道，从而接收频道中的消息和事件通知。

```cpp
// 方法调用
SubscribeOptions options;

uint64_t requestId;
rtm_client->subscribe("channelName", options, requestId);
```

调用该方法后，SDK 会触发 `onSubscribeResult` 回调并返回 API 调用结果。

```cpp
// 异步回调
class RtmEventHandler : public IRtmEventHandler {
    void onSubscribeResult(const uint64_t requestId, const char *channelName, RTM_ERROR_CODE errorCode) {
        if (errorCode != RTM_ERROR_OK) {
            printf("subscribe rtm channel failed error is %d reason is %s\n", errorCode, getErrorReason(errorCode));
        } else {
            printf("subscribe rtm channel %s success\n", channelName);
        }
    }
};
```

默认情况下，你会收到你所订阅的所有频道的消息事件。如果你无需接收某些特定频道的消息，但仍需接收这些频道中其他类型的事件通知或其他频道的消息，你可以将 `SubscribeOptions` 参数中的 `withMessage` 字段设置为 `false`。

```cpp
SubscribeOptions options;
options.withMessage = false;
options.withPresence = true;
options.withMetadata = true;
options.withLock = true;

uint64_t requestId;
rtmClient->subscribe("channelName", options, requestId);
```

`subscribe` 方法只允许你一次订阅一个频道。如需订阅多个频道，你可以多次调用该方法。例如，当你想同时订阅频道 `chats.room1` 和频道 `chats.room2` 时，你可以参考如下示例代码：

```cpp
SubscribeOptions options;
options.withMessage = false;
options.withPresence = true;
options.withMetadata = true;
options.withLock = true;

uint64_t requestId;
rtm_client->subscribe("chats.room1", options, requestId);
rtm_client->subscribe("chats.room2", options, requestId);
```
<_PlatformProcessedMarker close="true" />

<_PlatformProcessedMarker groupMode="structured" canonicalPlatform="web" platform="swift" />
监听了 `didReceiveMessageEvent` 事件通知后，你就可以调用 `subscribe` 方法订阅频道，从而接收频道中的消息和事件通知。

```swift
rtm?.subscribe(channelName: channel, option: nil, completion: { res, error in
        if error != nil {
            print("\(error?.operation) failed! error reason is \(error?.reason)")
        } else {
            print("success")
        }
    })
```

默认情况下，你会收到你所订阅的所有频道的消息事件。如果你无需接收某些特定频道的消息，但仍需接收这些频道中其他类型的事件通知或其他频道的消息，请勿将 `AgoraRtmSubscribeOptions` 参数中的 `features` 字段设为 `metadata`。

```swift
let option = AgoraRtmSubscribeOptions();
option.features = [.presence, .metadata, .lock]
rtm?.subscribe(channelName: channel, option: option, completion: { res, error in
        if error != nil {
            print("\(error?.operation) failed! error reason is \(error?.reason)")
        } else {
            print("success")
        }
    })
```

`subscribe` 方法只允许你一次订阅一个频道。如需订阅多个频道，你可以多次调用该方法。例如，当你想同时订阅频道 `chats.room1` 和频道 `chats.room2` 时，你可以参考如下示例代码：

```swift
rtm?.subscribe(channelName: channel1, option: nil, completion: { res, error in
        if error != nil {
            print("\(error?.operation) failed! error reason is \(error?.reason)")
        } else {
            print("success")
        }
    })
rtm?.subscribe(channelName: channel2, option: nil, completion: { res, error in
        if error != nil {
            print("\(error?.operation) failed! error reason is \(error?.reason)")
        } else {
            print("success")
        }
    })
```
<_PlatformProcessedMarker close="true" />

<_PlatformProcessedMarker groupMode="structured" canonicalPlatform="web" platform="mini-program" />
监听了 `message` 事件通知后，你就可以调用 `subscribe` 方法订阅频道，从而接收频道中的消息和事件通知。

```javascript
const options = {
    withMessage: true,
    withPresence: true,
    beQuiet : false,
    withMetadata: true,
    withLock: true,
};
const channelName = "test_channel";
try {
    const subscribeResult = await rtmClient.subscribe(channelName, options);
} catch (status) {
    const { operation, reason, errorCode } = status;
    console.log(`${operation} failed, the error code is ${errorCode}, due to: ${reason}.`);
}
```

默认情况下，你会收到你所订阅的所有频道的消息事件。如果你无需接收某些特定频道的消息，但仍需接收这些频道中其他类型的事件通知或其他频道的消息，你可以将 `SubscribeOptions` 参数中的 `withMessage` 字段设置为 `false`。

```javascript
const options = {
    withMessage: false,
    withPresence: true,
    withMetadata: true,
    withLock: true,
};
const channelName = "test_channel";
try {
    const subscribeResult = await rtmClient.subscribe(channelName, options);
} catch (status) {
    const { operation, reason, errorCode } = status;
    console.log(`${operation} failed, ErrorCode: ${errorCode}, due to: ${reason}.`);
}
```

`subscribe` 方法只允许你一次订阅一个频道。如需订阅多个频道，你可以多次调用该方法。例如，当你想同时订阅频道 `chats.room1` 和频道 `chats.room2` 时，你可以参考如下示例代码：

```javascript
const options = {
    withMessage: true,
    withPresence: true,
    beQuiet : false,
    withMetadata: true,
    withLock: true,
};
const channelName1 = "chats.room1";
const channelName2 = "chats.room2";

try {
    const result1 = await rtmClient.subscribe(channelName1, options);
    // your code
} catch (status) {
    const { operation, reason, errorCode } = status;
    console.log(`${operation} failed, the error code is ${errorCode}, due to: ${reason}.`);
}

try {
    const result2 = await rtmClient.subscribe(channelName2, options);
    // your code
} catch (status) {
    const { operation, reason, errorCode } = status;
    console.log(`${operation} failed, the error code is ${errorCode}, due to: ${reason}.`);
}
```
<_PlatformProcessedMarker close="true" />
</_PlatformTabsGroup>

RTM 支持单个客户端同时订阅 50 个 Message 频道，但考虑到客户端性能和带宽的限制，声网建议单个客户端同时订阅不超过 30 个 Message 频道。对于一些大型的或者活跃的频道，建议你根据实际情况进一步降低单个客户端同时订阅的频道数量。

## 取消订阅 [#取消订阅]

<_PlatformTabsGroup>
<_PlatformProcessedMarker groupMode="structured" canonicalPlatform="web" platform="android" />
如需停止接收某个频道中的所有消息和事件通知，你可以调用 `unsubscribe` 方法。

```java
String channelName = "chats.room1";
mRtmClient.unsubscribe(channelName, new ResultCallback<Void>() {
    @Override
    public void onSuccess(Void responseInfo) {
        log(CALLBACK, "unsubscribe channel " + channelName + " success");
    }

    @Override
    public void onFailure(ErrorInfo errorInfo) {
        log(ERROR, errorInfo.toString());
    }
});
```
<_PlatformProcessedMarker close="true" />

<_PlatformProcessedMarker groupMode="structured" canonicalPlatform="web" platform="ios" />
如需停止接收某个频道中的所有消息和事件通知，你可以调用 `unsubscribeWithChannel` 方法。

```objc
[rtm unsubscribeWithChannel:@"chats.room1" completion:^(AgoraRtmCommonResponse * _Nullable response, AgoraRtmErrorInfo * _Nullable errorInfo) {
    if (errorInfo == nil) {
        NSLog(@"unsubscribe success!!");
    } else {
        NSLog(@"unsubscribe failed, errorCode %d, reason %@", errorInfo.errorCode, errorInfo.reason);
    }
}];
```
<_PlatformProcessedMarker close="true" />

<_PlatformProcessedMarker groupMode="structured" canonicalPlatform="web" platform="web" />
如需停止接收某个频道中的所有消息和事件通知，你可以调用 `unsubscribe` 方法。

```javascript
const channelName = "chats.room1";
try {
    const result = await rtmClient.unsubscribe(channelName);
} catch (status) {
    const { operation, reason, errorCode } = status;
    console.log(`${operation} failed, ErrorCode: ${errorCode}, due to: ${reason}.`);
}
```
<_PlatformProcessedMarker close="true" />

<_PlatformProcessedMarker groupMode="structured" canonicalPlatform="web" platform="harmonyos" />
如需停止接收某个频道中的所有消息和事件通知，你可以调用 `unsubscribe` 方法。

```typescript
import { RtmError } from '@shengwang/rtm-full';

const channelName = "chats.room1";

try {
  const response = await rtmClient.unsubscribe(channelName);
  console.log("Unsubscribe channel success:", response);
} catch (error) {
  console.error("Unsubscribe failed:", error);
  if (error instanceof RtmError) {
    console.error(`Unsubscribe failed: ${error.reason} (code: ${error.errorCode})`);
  }
}
```
<_PlatformProcessedMarker close="true" />

<_PlatformProcessedMarker groupMode="structured" canonicalPlatform="web" platform="unity" />
如需停止接收某个频道中的所有消息和事件通知，你可以调用 `UnsubscribeAsync` 方法。

```csharp
var (status,response) = await rtmClient.UnsubscribeAsync("chats.room1");
if (status.Error)
{
    Debug.Log(string.Format("{0} is failed, ErrorCode: {1}, due to: {2}", status.Operation, status.ErrorCode, status.Reason));
}
```
<_PlatformProcessedMarker close="true" />

<_PlatformProcessedMarker groupMode="structured" canonicalPlatform="web" platform="flutter" />
如需停止接收某个频道中的所有消息和事件通知，你可以调用 `unsubscribe` 方法。

```dart
final channel = 'chat_room';
try {
    var (status, response) = await rtmClient.unsubscribe( channel );
    if (status.error == true ){
       print('${status.operation} failed, errorCode: ${status.errorCode}, due to ${status.reason}');
    } else {
        print('${status.operation} success!');
    }
} catch (e) {
    print('something went wrong: $e');
}
```
<_PlatformProcessedMarker close="true" />

<_PlatformProcessedMarker groupMode="structured" canonicalPlatform="web" platform="cpp" />
如需停止接收某个频道中的所有消息和事件通知，你可以调用 `unsubscribe` 方法。

```cpp
uint64_t requestId;
rtmClient->unsubscribe("chats.room1", requestId);
```

调用该方法后，SDK 会触发 `onUnsubscribeResult` 回调并返回 API 调用结果。

```cpp
class RtmEventHandler : public IRtmEventHandler {
    void onUnsubscribeResult(const uint64_t requestId, const char* channelName, RTM_ERROR_CODE errorCode) override {
        if (errorCode != RTM_ERROR_OK) {
            printf("unsubscribe rtm channel failed error is %d reason is %s\n", errorCode, getErrorReason(errorCode));
        } else {
            printf("unsubscribe rtm channel %s success\n", channelName);
        }
    }
};
```
<_PlatformProcessedMarker close="true" />

<_PlatformProcessedMarker groupMode="structured" canonicalPlatform="web" platform="swift" />
如需停止接收某个频道中的所有消息和事件通知，你可以调用 `unsubscribe` 方法。

```swift
RtmClient?.unsubscribe(channel) { res, error in
    if error != nil {
        print("\(error?.operation) failed! error reason is \(error?.reason)")
    } else {
        print("success")
    }
}
```
<_PlatformProcessedMarker close="true" />

<_PlatformProcessedMarker groupMode="structured" canonicalPlatform="web" platform="mini-program" />
如需停止接收某个频道中的所有消息和事件通知，你可以调用 `unsubscribe` 方法。

```javascript
const channelName = "chats.room1";
try {
    const result = await rtmClient.unsubscribe(channelName);
} catch (status) {
    const { operation, reason, errorCode } = status;
    console.log(`${operation} failed, ErrorCode: ${errorCode}, due to: ${reason}.`);
}
```
<_PlatformProcessedMarker close="true" />
</_PlatformTabsGroup>

该方法一次只能取消订阅一个频道。如需同时取消订阅多个频道，你需要多次调用该方法。