# Traffic Management

## Introduction

The traffic management module allows you to query real-time or historical data traffic by the specified network interface card (NIC) or user ID (UID).

Its functions include:

- Obtaining real-time traffic data by NIC or UID
- Obtaining historical traffic data by NIC or UID
- Subscribing to traffic change events by NIC or UID

> **NOTE**
> 
> To maximize the application running efficiency, most API calls are called asynchronously in callback or promise mode. The following code examples use the callback mode. For details about the APIs, see [Traffic Management](../reference/apis/js-apis-net-statistics.md).

The following describes the development procedure specific to each application scenario.

## Available APIs

For the complete list of APIs and example code, see [Traffic Management](../reference/apis/js-apis-net-statistics.md).

| Type| API| Description|
| ---- | ---- | ---- |
| ohos.net.statistics | getIfaceRxBytes(nic: string, callback: AsyncCallback\<number>): void; |Obtains the real-time downlink data traffic of the specified NIC. |
| ohos.net.statistics | getIfaceTxBytes(nic: string, callback: AsyncCallback\<number>): void; |Obtains the real-time uplink data traffic of the specified NIC. |
| ohos.net.statistics | getCellularRxBytes(callback: AsyncCallback\<number>): void; |Obtains the real-time downlink data traffic of the cellular network.|
| ohos.net.statistics | getCellularTxBytes(callback: AsyncCallback\<number>): void; |Obtains the real-time uplink data traffic of the cellular network.|
| ohos.net.statistics | getAllRxBytes(callback: AsyncCallback\<number>): void; |Obtains the real-time downlink data traffic of the all NICs. |
| ohos.net.statistics | getAllTxBytes(callback: AsyncCallback\<number>): void; |Obtains the real-time uplink data traffic of the all NICs. |
| ohos.net.statistics | getUidRxBytes(uid: number, callback: AsyncCallback\<number>): void; |Obtains the real-time downlink data traffic of the specified application. |
| ohos.net.statistics | getUidTxBytes(uid: number, callback: AsyncCallback\<number>): void; |Obtains the real-time uplink data traffic of the specified application. |
| ohos.net.statistics | getTrafficStatsByIface(ifaceInfo: IfaceInfo, callback: AsyncCallback\<NetStatsInfo>): void; |Obtains the historical data traffic of the specified NIC. |
| ohos.net.statistics | getTrafficStatsByUid(uidInfo: UidInfo, callback: AsyncCallback\<NetStatsInfo>): void; |Obtains the historical data traffic of the specified application. |
| ohos.net.statistics | on(type: 'netStatsChange', callback: Callback\<{ iface: string, uid?: number }>): void |Subscribes to traffic change events.|
| ohos.net.statistics | off(type: 'netStatsChange', callback?: Callback\<{ iface: string, uid?: number }>): void; |Unsubscribes from traffic change events.|

## Obtaining Real-Time Traffic Data by NIC or UID

1. Obtain the real-time data traffic of the specified NIC. 
2. Obtain the real-time data traffic of the cellular network.
3. Obtain the real-time data traffic of all NICs. 
4. Obtain the real-time data traffic of the specified application. 

```js
// Import the statistics namespace from @ohos.net.statistics.
import statistics from '@ohos.net.statistics'

// Obtain the real-time downlink data traffic of the specified NIC. 
statistics.getIfaceRxBytes("wlan0", (error, stats) => {
    console.log(JSON.stringify(error))
    console.log(JSON.stringify(stats))
})

// Obtain the real-time uplink data traffic of the specified NIC. 
statistics.getIfaceTxBytes("wlan0", (error, stats) => {
    console.log(JSON.stringify(error))
    console.log(JSON.stringify(stats))
})

// Obtain the real-time downlink data traffic of the cellular network.
statistics.getCellularRxBytes((error, stats) => {
    console.log(JSON.stringify(error))
    console.log(JSON.stringify(stats))
})

// Obtain the real-time uplink data traffic of the cellular network.
statistics.getCellularTxBytes((error, stats) => {
    console.log(JSON.stringify(error))
    console.log(JSON.stringify(stats))
})

// Obtain the real-time downlink data traffic of the all NICs. 
statistics.getAllRxBytes((error, stats) => {
    console.log(JSON.stringify(error))
    console.log(JSON.stringify(stats))
})

// Obtain the real-time uplink data traffic of the all NICs. 
statistics.getAllTxBytes((error, stats) => {
    console.log(JSON.stringify(error))
    console.log(JSON.stringify(stats))
})

// Obtain the real-time downlink data traffic of the specified application. 
let uid = 20010038;
statistics.getUidRxBytes(uid, (error, stats) => {
    console.log(JSON.stringify(error))
    console.log(JSON.stringify(stats))
})

// Obtain the real-time uplink data traffic of the specified application. 
let uid = 20010038;
statistics.getUidTxBytes(uid, (error, stats) => {
    console.log(JSON.stringify(error))
    console.log(JSON.stringify(stats))
})
```

## Obtaining Historical Traffic Data by NIC or UID

1. Obtain the historical data traffic of the specified NIC. 
2. Obtain the historical data traffic of the specified application. 

```js
let ifaceInfo = {
    iface: "wlan0",
    startTime: 1685948465,
    endTime: 16859485670
}
// Obtain the historical data traffic of the specified NIC. 
statistics.getTrafficStatsByIface(ifaceInfo), (error, statsInfo) => {
    console.log(JSON.stringify(error))
    console.log("getTrafficStatsByIface bytes of received = " + JSON.stringify(statsInfo.rxBytes));
    console.log("getTrafficStatsByIface bytes of sent = " + JSON.stringify(statsInfo.txBytes));
    console.log("getTrafficStatsByIface packets of received = " + JSON.stringify(statsInfo.rxPackets));
    console.log("getTrafficStatsByIface packets of sent = " + JSON.stringify(statsInfo.txPackets));
});

let uidInfo = {
    ifaceInfo: {
      iface: "wlan0",
      startTime: 1685948465,
      endTime: 16859485670
    },
    uid: 20010037
}
// Obtain the historical data traffic of the specified application. 
statistics.getTrafficStatsByUid(uidInfo), (error, statsInfo) => {
    console.log(JSON.stringify(error))
    console.log("getTrafficStatsByUid bytes of received = " + JSON.stringify(statsInfo.rxBytes));
    console.log("getTrafficStatsByUid bytes of sent = " + JSON.stringify(statsInfo.txBytes));
    console.log("getTrafficStatsByUid packets of received = " + JSON.stringify(statsInfo.rxPackets));
    console.log("getTrafficStatsByUid packets of sent = " + JSON.stringify(statsInfo.txPackets));
});

```

## Subscribing to Traffic Change Events

1. Subscribe to traffic change events.
2. Unsubscribe from traffic change events.

```js

let callback = data => {
    console.log("on netStatsChange, data:" + JSON.stringify(data));
}
// Subscribe to traffic change events.
statistics.on('netStatsChange', callback);

// Unsubscribe from traffic change events. You can pass the callback of the **on** function if you want to unsubscribe from a certain type of event. If you do not pass the callback, you will unsubscribe from all events.
statistics.off('netStatsChange', callback);
statistics.off('netStatsChange');

```