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The main content of this article is to explain "what is the method of mqtt transplantation", interested friends may wish to have a look. The method introduced in this paper is simple, fast and practical. Let's let the editor take you to learn "what is the method of mqtt transplantation"?

Transplant environment

Ubuntu: ubuntu16.04 provided by Xunwei

Compiler: arm-2014.05-29-arm-none-linux-gnueabi-i686-pc-linux-gnu.tar.bz2

MOTT introduction

MQTT (Message Queuing Telemetry Transport, message queuing Telemetry Transport Protocol) is a basic

A lightweight protocol in publish / subscribe (publish/subscribe) mode, which is built on top of the TCP/IP protocol

The biggest advantage of MQTT is that it can provide real-time and reliable elimination for connecting remote devices with very little code and limited bandwidth.

Information service. As an instant messaging protocol with low overhead and low bandwidth consumption, it can be used in Internet of things, small devices and mobile applications.

It is widely used in many aspects.

What we are using here is that Mosquitto,Mosquitto is the implementation of MQTT, because MQTT is a

Agreement is like the relationship between Linux and Ubuntu. Ubuntu is one of the distributions of Linux, and Mosquitto is

One of the implementation methods of MQTT, why do we use Mosquitto instead of other implementation methods here?

Because Mosquitto is powerful, it can be used not only as a publisher and subscriber of messages, but also as a server. Other

He has almost all the functions that the worker has, so we use Mosquitto.

one。 Install mosquitto on X86

Install mosquitto using apt-get with the following command:

Apt-get install mosquitto

Install the mosquitto client with the following command:

Apt-get install mosquitto-clients

two。 Test mosquitto on x86

We are now doing simple tests on the native X86 and are familiar with the relevant commands.

Test steps:

(1) start the service mosquitto

(2) subscribers subscribe to messages for specified topics through mosquitto_sub.

(3) the publisher publishes messages for the specified topic through mosquitto_pub.

Step one

Start the mosquitto service with the following command:

Service mosquitto start

To see if mosquitto starts successfully, the command is as follows:

Ps-ef | grep mosquitto

The successful startup is shown in the following figure:

Step two

Open a terminal and subscribe to the topic with the following command:

Mosquitto_sub-h localhost-t "mqtt"-v

The parameter-h is the MQTT server to which you want to connect. Here, you can use the native IP,-t subscription topic directly, here it is mqtt, so the topic prints more debugging information for mqtt,-v.

As shown in the following figure:

Step three

Open another terminal and (note that we have opened a new terminal here) release the topic with the following command:

Mosquitto_pub-h localhost-t "mqtt"-m "Hello MQTT"

Parameter-h is the specified MQTT server to connect to, which is connected locally, so it is localhost, and also

It can be the IP address of the device to be connected,-t subscribe to the topic, where the message content is specified for the mqtt,-m, and here the Hello MQTT is sent.

As shown in the following figure:

After the delivery is successful, the subscriber of mqtt will receive the information Hello MQTT of our publication, as shown below:

three。 Migrate mosquitto to development board

Mqtt source code download page:

Https://mosquitto.org/files/source/

The Mosquitto library depends on libuuid and openssl libraries, so we need to cross-compile the dependent libraries he needs before cross-compiling Mosquitto. Here, the author has downloaded all the source code he needs, and you can find it in the directory of this document. It is not recommended that you download a version that is inconsistent with me, there may be problems.

1. Cross-compile uuid library

We copied the source code of uuid to Ubuntu, and the author copied it to / home/topeet/mqtt, as shown below:

Enter the following command to extract the source code and enter the folder generated by the decompression:

Tar-vxf libuuid-1.0.3.tar.gz

As shown in the following figure:

Then we create a folder called mosquitto-arm under / opt/ with the following command:

Mkdir-p / opt/mosquitto-arm

As shown in the following figure:

To configure the source code, enter the following command in the folder where the generated uuid library is extracted:

. / configure-prefix=/opt/mosquitto-arm/libuuid-1.0.3 CC=arm-none-linux-gnueabi-gcc-host=arm-linux

As shown in the following figure:

Finally, compile and install, with the following command:

Make

Make install

After compiling and installing successfully, we will get a folder of libuuid under our setting / opt/mosquitto-arm.

two。 Cross-compile openssl library

Decompress the package into the directory after decompression

Tar-vxf openssl-1.0.2g.tar.gz cd openssl-1.0.2g

This is shown in the following figure. The author is placed in the / home/topeet/mqtt directory

Configure compilation parameters

Setarch i386. / config no-asm shared-- prefix=/opt/mosquitto-arm/openssl/

Setarch i386: declare that a 32-bit CPU is generated, and remove this part if it is a 64-bit CPU

-- prefix: specify the path to the generated directory after make install. If this item is not modified, the default is OPENSSLDIR.

Directory (/ usr/local/ssl).

Shared: generate dynamic link libraries.

No-asm: does not use assembly code to speed up the compilation process during cross-compilation, because its assembly code does not support the arm format

Delete-M32 and-M64 if there is-M32 and-M64 in Makefile, but not in my Makefile.

As shown in the following figure:

Modify the compiler parameters in Makefile under the openss folder as follows

CC= arm-none-linux-gnueabi-gcc

AR= arm-none-linux-gnueabi-ar $(ARFLAGS) r

RANLIB= arm-none-linux-gnueabi-ranlib

NM= arm-none-linux-gnueabi-nm

As shown in the following figure:

Compile and install

Make

Make install

After compiling and installing successfully, we will get a folder of openssl under our setting / opt/mosquitto-arm.

3. Cross-compile mosquitto

Decompress the package into the directory after decompression

Tar-vxf mosquitto-1.5.tar.gz cd mosquitto-1.5

This is shown in the following figure. The author is placed in the / home/topeet/mqtt directory

Compile source code

Make WITH_SRV=no CC=arm-none-linux-gnueabi-gcc CXX=arm-none-linux-gnueabi-g++

CFLAGS= "- I/opt/mosquitto-arm/openssl/ include-I/opt/mosquitto-arm/ libuuid-1.0.3/include-I/opt/mosquitto-arm/openssl/lib-I/opt/mosquit / to-arm/libuuid-1.0.3/lib" LDFLAGS= "- L

/ opt/mosquitto-arm/openssl/lib-L / opt/mosquitto-arm/libuuid-1.0.3/lib-lssl-lcrypto-luuid "

Note that if the path of installing uuid and openssl libraries here is not the same as mine, refer to-I and-L

Change the path of the specified library and header file to the path where you install the uuid and openssl libraries, otherwise you won't be able to compile.

As shown in the following figure:

The successful compilation is shown in the following figure:

To install, the command is as follows

Make DESTDIR=/opt/mosquitto-arm/mosquitto-1.5 install

After compiling and installing successfully, we will get a folder of mosquitto-1.5 under our setting / opt/mosquitto-arm.

At this point, I believe you have a deeper understanding of "what is the method of mqtt migration?" you might as well do it in practice. Here is the website, more related content can enter the relevant channels to inquire, follow us, continue to learn!

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