1# Network Connection Development
2
3## When to Use
4
5The **NetConnection** module provides the capability of querying common network information.
6
7## Available APIs
8
9The following table lists the common **NetConnection** APIs. For details, see [NetConnection](../reference/apis-network-kit/_net_connection.md).
10
11
12| API| **Test Description**|
13| -------- | -------- |
14| OH_NetConn_HasDefaultNet(int32_t \*hasDefaultNet) | Checks whether the default data network is activated and determines whether a network connection is available.|
15| OH_NetConn_GetDefaultNet(NetConn_NetHandle \*netHandle) | Obtains the default active data network.|
16| OH_NetConn_IsDefaultNetMetered(int32_t \*isMetered) | Checks whether the data traffic usage on the current network is metered.|
17| OH_NetConn_GetConnectionProperties(NetConn_NetHandle \*netHandle, NetConn_ConnectionProperties *prop) | Obtains network connection information based on the specified **netHandle**.|
18| OH_NetConn_GetNetCapabilities (NetConn_NetHandle \*netHandle, NetConn_NetCapabilities \*netCapacities) | Obtains network capability information based on the specified **netHandle**.|
19| OH_NetConn_GetDefaultHttpProxy (NetConn_HttpProxy \*httpProxy) | Obtains the default HTTP proxy configuration of the network. If the global proxy is set, the global HTTP proxy configuration is returned. If the application has been bound to the network specified by **netHandle**, the HTTP proxy configuration of this network is returned. In other cases, the HTTP proxy configuration of the default network is returned.|
20| OH_NetConn_GetAddrInfo (char \*host, char \*serv, struct addrinfo \*hint, struct addrinfo \*\*res, int32_t netId) | Obtains the DNS result based on the specified **netId**.|
21| OH_NetConn_FreeDnsResult(struct addrinfo \*res) | Releases the DNS query result.|
22| OH_NetConn_GetAllNets(NetConn_NetHandleList \*netHandleList) | Obtains the list of all connected networks.|
23| OHOS_NetConn_RegisterDnsResolver(OH_NetConn_CustomDnsResolver resolver) | Registers a custom DNS resolver.<br>Note: This API is deprecated since API version 13.<br>You are advised to use **OH_NetConn_RegisterDnsResolver** instead.|
24| OHOS_NetConn_UnregisterDnsResolver(void) | Unregisters a custom DNS resolver.<br>Note: This API is deprecated since API version 13.<br>You are advised to use **OH_NetConn_UnregisterDnsResolver** instead.|
25| OH_NetConn_RegisterDnsResolver(OH_NetConn_CustomDnsResolver resolver) | Registers a custom DNS resolver.|
26| OH_NetConn_UnregisterDnsResolver(void) | Unregisters a custom DNS resolver.|
27
28## Development Example
29
30### How to Develop
31
32To use related APIs to obtain network information, you need to create a Native C++ project, encapsulate the APIs in the source file, and call these APIs at the ArkTs layer. You can use hilog or console.log to print the log information on the console or generate device logs.
33
34This document describes how to obtain the default active data network as an example.
35
36### Adding Dependencies
37
38**Adding the Dynamic Link Library**
39
40Add the following library to **CMakeLists.txt**.
41
42```txt
43libace_napi.z.so
44libnet_connection.so
45```
46
47**Including Header Files**
48
49```c
50#include "napi/native_api.h"
51#include "network/netmanager/net_connection.h"
52#include "network/netmanager/net_connection_type.h"
53```
54
55### Building the Project
56
571. Write the code for calling the API in the source file, encapsulate it into a value of the `napi_value` type, and return the value to the Node.js environment.
58
59```C
60// Get the execution results of the default network connection.
61static napi_value GetDefaultNet(napi_env env, napi_callback_info info)
62{
63    size_t argc = 1;
64    napi_value args[1] = {nullptr};
65    napi_get_cb_info(env, info, &argc, args, nullptr, nullptr);
66    int32_t param;
67    napi_get_value_int32(env, args[0], &param);
68
69    NetConn_NetHandle netHandle;
70    if (param== 0) {
71        param= OH_NetConn_GetDefaultNet(NULL);
72    } else {
73        param= OH_NetConn_GetDefaultNet(&netHandle);
74    }
75
76    napi_value result;
77    napi_create_int32(env, param, &result);
78    return result;
79}
80
81// Get the ID of the default network connection.
82static napi_value NetId(napi_env env, napi_callback_info info) {
83    int32_t defaultNetId;
84
85    NetConn_NetHandle netHandle;
86    OH_NetConn_GetDefaultNet(&netHandle);
87    defaultNetId = netHandle.netId; // Get the default netId
88
89    napi_value result;
90    napi_create_int32(env, defaultNetId, &result);
91
92    return result;
93}
94```
95
96> **NOTE**<br>The two functions are used to obtain information about the default network connection of the system. Wherein, GetDefaultNet is used to receive the test parameters passed from ArkTs and return the corresponding return value after the API is called. You can change param as needed. If the return value is **0**, the parameters are obtained successfully. If the return value is **401**, the parameters are incorrect. If the return value is **201**, the user does not have the operation permission. NetId indicates the ID of the default network connection. You can use the information for further network operations.
97
98
992. Initialize and export the `napi_value` objects encapsulated through **NAPI**, and expose the preceding two functions to JavaScript through external function APIs.
100
101```C
102EXTERN_C_START
103static napi_value Init(napi_env env, napi_value exports)
104{
105    // Information used to describe an exported attribute. Two properties are defined here: `GetDefaultNet` and `NetId`.
106    napi_property_descriptor desc[] = {
107        {"GetDefaultNet", nullptr, GetDefaultNet, nullptr, nullptr, nullptr, napi_default, nullptr},
108        {"NetId", nullptr, NetId, nullptr, nullptr, nullptr, napi_default, nullptr}};
109    napi_define_properties(env, exports, sizeof(desc) / sizeof(desc[0]), desc);
110    return exports;
111}
112EXTERN_C_END
113```
114
1153. Register the objects successfully initialized in the previous step into the Node.js file by using the `napi_module_register` function of `RegisterEntryModule`.
116
117```C
118static napi_module demoModule = {
119    .nm_version = 1,
120    .nm_flags = 0,
121    .nm_filename = nullptr,
122    .nm_register_func = Init,
123    .nm_modname = "entry",
124    .nm_priv = ((void*)0),
125    .reserved = { 0 },
126};
127
128extern "C" __attribute__((constructor)) void RegisterEntryModule(void)
129{
130    napi_module_register(&demoModule);
131}
132```
133
1344. Define the types of the two functions in the `index.d.ts ` file of the project.
135
136- The `GetDefaultNet ` function accepts the numeric parameter code and returns a numeric value.
137- The `NetId` function does not accept parameters and returns a numeric value.
138
139```ts
140export const GetDefaultNet: (code: number) => number;
141export const NetId: () => number;
142```
143
1445. Call the encapsulated APIs in the `index.ets` file.
145
146```ts
147import testNetManager from 'libentry.so';
148
149@Entry
150@Component
151struct Index {
152  @State message: string = '';
153
154  build() {
155    Row() {
156      Column() {
157        Text(this.message)
158          .fontSize(50)
159          .fontWeight(FontWeight.Bold)
160        Button('GetDefaultNet').onClick(event => {
161          this.GetDefaultNet();
162        })
163        Button('CodeNumber').onClick(event =>{
164          this.CodeNumber();
165        })
166      }
167      .width('100%')
168    }
169    .height('100%')
170  }
171
172  GetDefaultNet() {
173    let netid = testNetManager.NetId();
174    console.log("The defaultNetId is [" + netid + "]");
175  }
176
177  CodeNumber() {
178    let testParam = 0;
179    let codeNumber = testNetManager.GetDefaultNet(testParam);
180    if (codeNumber === 0) {
181      console.log("Test success. [" + codeNumber + "]");
182    } else if (codeNumber === 201) {
183      console.log("Missing permissions. [" + codeNumber + "]");
184    } else if (codeNumber === 401) {
185      console.log("Parameter error. [" + codeNumber + "]");
186    }
187  }
188}
189
190```
191
1926. Configure the `CMakeLists.txt` file. Add the required shared library, that is, `libnet_connection.so`, to `target_link_libraries` in the `CMakeLists.txt` file automatically generated by the project.
193
194Note: As shown in the following figure, `entry` in `add_library` is the modename automatically generated by the project. If you want to change the `modename`, ensure that it is the same as the `.nm_modname` in step 3.
195
196![netmanager-4.png](./figures/netmanager-4.png)
197
198After the preceding steps, the entire project is set up. Then, you can connect to the device to run the project to view logs.
199
200## **Test Procedure**
201
2021. Connect the device and use DevEco Studio to open the project.
203
2042. Run the project. The following figure is displayed on the device.
205
206> NOTE
207
208- If you click `GetDefaultNet`, you'll obtain the default network ID.
209- If you click `codeNumber`, you'll obtain the status code returned by the API.
210
211![netmanager-1.png](./figures/netmanager-1.png)
212
2133. Click `GetDefaultNet`. The following log is displayed, as shown below:
214
215![netmanager-2.png](./figures/netmanager-2.png)
216
2174. Click `codeNumber`. The status code is displayed, as shown below:
218
219![netmanager-3.png](./figures/netmanager-3.png)
220