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:

• 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{

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.bt_check_SD:
                Thread t_ck_sd = new Thread(){
                    @Override
                    public 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(){
                    @Override
                    public 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：