Shulou(Shulou.com)06/01 Report--

What this article shares with you is about how NDK makes an Android executive program. The editor thinks it is very practical, so I share it with you to learn. I hope you can get something after reading this article.

Preface

How to implement tracerout in Android, because most Android systems do not have the traceroute command, so they can only use ping to simulate.

For example, the-t command of ping can set up ttl, gradually increase debugging, and test each route.

But the efficiency is very low, I want to write a method with c

I used ndk to make a so, in which I used rawsocket to implement the icmp function, but found that there were insufficient permissions to establish a socket.

Access to the data found that Android can not run rawsocket without root permission.

Found a way to solve it.

Https://blog.csdn.net/Inconsolabl/article/details/50437588

Put the binaries into user space, and then set permissions 700

-rwx- (700)-- only owners have read, write, and execute permissions.

The experiment is successful, find a cross-compiled traceout on the Internet and seal it in app and call it directly.

Recently, I need to do another tcpping function, but I can't find a ready-made cross-compiled binary. In fact, tcpping is just a handshake probe, which can also be written with java. But java was busy, so I tried to write a cross-compiled tcpping.

Realize

Https://blog.csdn.net/qushaobo/article/details/81089466

An example is written with reference to the code.

But cannot be executed, display

". / data/user/0/com.example.myapplication/files/tcpping": error: Android 5.0and later only support position-independent executables (- fPIE).

It is found that the example code is

# include # include # include int main (int argc, char * argv []) {fprintf (stderr, "this is a test...\ n"); return 0;}

Using stderr, it is possible that Android's permissions are very strict, and it is not possible to output to standard error, so change it to printf and ok.

Format

Some compatibility changes have been made to the example code

Android.mk:

LOCAL_PATH: = $(call my-dir) include $(CLEAR_VARS) LOCAL_MODULE: = tcppingLOCAL_SRC_FILES: = tcpping.cppifeq ($(TARGET_ARCH_ABI), armeabi-v7a) LOCAL_CFLAGS + =-LOCAL_CFLAGS: = armelse LOCAL_ARM_MODE: = armendif# compatible 5.0+LOCAL_CFLAGS + =-fPIE-fPICLOCAL_LDFLAGS + =-fPIE-pieinclude $(BUILD_EXECUTABLE)

Application.mk

APP_STL: = gnustl_static

APP_CPPFLAGS: =-frtti-fexceptions

APP_ABI: = armeabi armeabi-v7a x86

APP_PLATFORM: = android-14

Compile

$NDK/ndk-build DK_DEBUG=1-B Vista 1

Go to the libs directory and get the execution program of tcpping binary on three platforms

This is how NDK makes an Android executive program. The editor believes that there are some knowledge points that we may see or use in our daily work. I hope you can learn more from this article. For more details, please follow the industry information channel.

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