Android: 在wsl中使用libevent实现http服务器，并编写Android app 实现文件下载

在wsl中使用libevent实现http服务器，并编写Android app 实现文件下载

PC端：

• 在WSL中编译libevent-2.1.8-stable sample中的http-server.c，实现http测试用服务器

• Makefile如下：

#指定源文件为*.c
src = $(wildcard *.c)
#通过src生成中间需要的汇编文件名，把src中.c替换为.o
obj = $(patsubst %.c, %.o, $(src))

#指定最后生成的可执行文件a.out
target = http-server

#ALL代表搜索依赖，一直查找到文件尾部
ALL:$(target)

#再链接汇编文件生成可执行文件a.out
$(target):$(obj)
gcc $^ -o $@ -L./ -ljson-c -L./ -levent
#-L./ -levent
#-L./ -lpthread
#-L./ -lpthread

#先生成汇编文件.o
%.o:%c
gcc -c $< -o $@

#clean命令,清除目标文件(a.out)和中间生成的汇编文件(*.o)
clean:
-rm -rf $(target) $(obj)

#生成伪目标，防止makefile所在文件目录中有clean, a.out等干扰文件
.PHONY : clean ALL

• 注意启动时要加上服务器默认的文件目录，这里是dump

• 服务器默认的文件目录内容如下：

Android Studio端：

• AndroidMainfest 添加权限

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

• activity_main.xml文件:

<?xml version="1.0" encoding="utf-8"?>

<Buttonandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:id="@+id/bt_check_SD"android:text="检测SD卡"/>
<Buttonandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:id="@+id/bt_download_file"android:layout_below="@+id/bt_check_SD"android:text="下载文件"/><TextViewandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:text="Hello World!"android:layout_below="@id/bt_download_file"app:layout_constraintBottom_toBottomOf="parent"app:layout_constraintEnd_toEndOf="parent"app:layout_constraintStart_toStartOf="parent"app:layout_constraintTop_toTopOf="parent" />

• MainActivity.java文件:

package com.example.file_download;

import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;

import android.Manifest;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

public class MainActivity extends AppCompatActivity {
private String TAG = "MainActivity: ";
private String urlLoadPath = “http://10.0.2.2:7777/test.txt”; //下载的文件 网络地址
private String savaDirPath = “testLoad”; //保存的地址

@Override
protected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);View.OnClickListener myClickListener = new MyClickListener();Button bt_ck = findViewById(R.id.bt_check_SD);Button bt_dw = findViewById(R.id.bt_download_file);bt_ck.setOnClickListener(myClickListener);bt_dw.setOnClickListener(myClickListener);}
private class MyClickListener implements View.OnClickListener{@Overridepublic void onClick(View v) {switch (v.getId()) {case R.id.bt_check_SD:Thread t_ck_sd = new Thread(){@Overridepublic void run() {Log.e(TAG," checkPermission run");checkPermission();}};t_ck_sd.start();Toast.makeText(MainActivity.this, "bt_ck", Toast.LENGTH_SHORT).show();break;case R.id.bt_download_file:Thread t_dw_file = new Thread(){@Overridepublic void run() {Log.e(TAG," DownLoadFileFormUrl run");DownLoadFileFormUrl(urlLoadPath,savaDirPath);}};t_dw_file.start();Toast.makeText(MainActivity.this,"bt_download_file",Toast.LENGTH_SHORT).show();break;default:break;}}
}//sd 卡权限申请
private void checkPermission() {if (ActivityCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE)!= PackageManager.PERMISSION_GRANTED) {ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE},100);}return;
}public boolean DownLoadFileFormUrl(String urlLoadPath, String savaDirPath){InputStream inputStream = null;FileOutputStream fileOutputStream = null;HttpURLConnection httpURLConnection = null;if (!Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())) {Log.i(TAG," 未安装 SD 卡");return  false;}File pathSd = Environment.getExternalStorageDirectory();  //获取 SD 卡路径File fileRealDirectoty  = new File(pathSd.getAbsolutePath() + File.separator + savaDirPath);Log.i(TAG,"文件保存的真正目录： " + fileRealDirectoty);if (!fileRealDirectoty.exists()) {  //如果目录 不存在 ，就创建Log.i(TAG,"创建 存储文件夹");fileRealDirectoty.mkdirs();}//获取要下载的文件名称，在这里可以更改下载的文件名String fileName = urlLoadPath.substring(urlLoadPath.lastIndexOf("/") + 1);//String fileName = "test.zip";//创建 这个文件名 命名的 file 对象File file = new File(fileRealDirectoty,fileName);Log.i(TAG,"file: " + file);if (!file.exists()) {  //倘若没有这个文件try {Log.i(TAG,"创建文件");file.createNewFile();  //创建这个文件} catch (IOException e) {e.printStackTrace();}}try {URL url = new URL(urlLoadPath);httpURLConnection = (HttpURLConnection) url.openConnection();httpURLConnection.connect();int code = httpURLConnection.getResponseCode();if (code == 200) {//网络连接成功} else {//网络返回异常}//根据响应获取文件大小int fileSize = httpURLConnection.getContentLength();Log.i(TAG,"文件大小： " + fileSize);inputStream = httpURLConnection.getInputStream();fileOutputStream = new FileOutputStream(file);byte[] b = new byte[1024];int tem = 0;while ((tem = inputStream.read(b))!= -1) {fileOutputStream.write(b,0,tem);}} catch (MalformedURLException e) {e.printStackTrace();return false;} catch (IOException e) {e.printStackTrace();return false;} finally {try {if (inputStream != null) {inputStream.close();}if (fileOutputStream != null) {fileOutputStream.close();}if (httpURLConnection != null) {httpURLConnection.disconnect();}} catch (IOException e) {e.printStackTrace();}}Log.i(TAG,"文件下载 成功");return true;
}

}

Android端结果：

在Device Manager中找到/storage/emulated/0/testLoad这个目录可以看到下载的文件。

PC端 结果：