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In our previous lesson we were able to send the commands from the laptop to the drone.

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In this lesson we will be writing code so we can receive the response from the drone to the laptop.

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When we are sending commands the drone we are able to handle when and what to send to the drone although

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when receiving a response from the drone we wouldn't be able to manage the timing to be able to receive

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the response.

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We will use a thread and create a while loop.

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Once the laptop receives a response it will receive the data and leave a log to use the thread.

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We have to import threading according to the pep 8 format.

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It's best that that libraries are imported in alphabetical order so threading will come between sis

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and time.

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Now let's go on and add codes to receive the response before getting into it.

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We've created socket said 2 with a binary command but since we created a set and command method we can

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rewrite this with a send command and command.

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We can do the same for a stream on now we're ready to set the response codes first we set self response

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to a noun.

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Here we want to use a thread.

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In this case we want to stop the thread.

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When an event occurs set self stop event and use threading event once we set the two codes we need to

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define a method to receive the response.

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The method name will be received response and set the argument as stop event.

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Also we said a while loop that will go on until the stop event occurs.

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Once the stop event occurs the loop should break.

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Next we set.

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Try self response.

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Currently unknown.

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We set the IP as self socket received from and we set a buffer size to three thousand.

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This three thousand is the same as a sample code in the Tello document.

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You can also set it to a thousand twenty four.

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Once we receive a response we want to use the logger info to print it out.

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Let's set action to receive response and response to self response in case a socket error occurs.

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We also want to log the error so we set an exception to socket error as the ex set the logger to log

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the error.

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Action will be received response an exception will be x.

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In this case if an error occurs let's break the loop.

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If an error occurs we may not be able to receive any responses so we should finish the loop.

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Next we will run this method with the thread set response thread to threading thread for the target

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we set self receive response.

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As this is a thread we won't need to follow with the parentheses.

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Now we set ARGs and set the argument as self stop event.

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Next we set the argument as a tuple type.

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At last we set the response thread to start we might be using the response thread later on.

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So we will add self-taught underscore before the method name to keep it private.

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The timing to invoke the stop event.

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We need to set it to under the stop method.

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We need to set self stop event except once the drone stops the stop event is set so that the while loop

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will end and your laptop won't receive any more responses.

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Let's scroll down to the bottom of the script after the drone manager commands to land the drone.

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We need to stop the drone manager once the stop is invoked.

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Stop underscore event dot set will invoke.

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Now I want to take a moment to briefly explain how the thread works especially for those of you who

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are not familiar with it.

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Here we set threading thread method to process multiple methods at once.

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We set the target to the method name.

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In this case it'll be received response when we set the args.

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We need to add a comma and the end to create a tuple type.

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If we don't set a comma this will become a single stop event as we create the thread we set it to start

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by running the received response method within a thread.

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This method will process what other methods are processed.

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The while loop will go on until this stop event occurs and while the loop is going on we will continue

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receiving the responses from the drone and set the data into response which will be logged by the logger.

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Let's go up the script a bit.

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We need to set the command and stream on after the thread starts so let's move the two methods here.

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Now let's run the code once we run the code.

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You can see that we are getting the log data.

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The log is showing the take off command which was received and responded OK.

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Now we see the drone land but we also see an error the error says bad file descriptor.

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Let's go back to the script to see why we got an error.

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The stop event method was invoked and broke the while loop.

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The drone was trying to send back a response but at the same time since the method is running on a thread

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the socket close method was also invoked.

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This means the drone was trying to send a response to a closed socket.

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This became the reason for the error to occur.

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To solve this problem once the stop event method is invoked we need to wait until the loop comes to

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an end.

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Then close the socket.

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We can set the system to sleep for a few seconds but in this case we want to be sure that the thread

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has finished before we close the socket.

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We set while self response thread is alive we will set the time sleep with point 3 seconds

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if the retrial goes up to 30.

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We understand it as a time up and break the loop.

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If not we can't count up one now we've completed our code so let's try running the code again once we

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run this code you will see that the command being sent and also the response from the drone is OK.

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Now the Land Command has been set and the drone lands sending the response as OK.

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This time there are no errors as we are running the process on thread the log data is showing three

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okays altogether.

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The responses should be paired with each commands.

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Let's rewrite the code so the log comes out cleaner.

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Go to the send command method set retry to zero.

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This will be similar to what we did with the self socket clothes we set while self response is none.

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We will set the time sleep with point three seconds if the retrial goes up to three we break the loop.

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If not we can count up one Next of self response is none the above was when the retrial became more

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than three.

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But this next if statement will be set for when the retrial is less than three response will be set

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temporarily to none.

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If the response is received else response will be set to self response decode UTF 8 for the self response.

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We want to initialize it back to none.

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We set to return the response that is set and the temporary response.

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Now the code is ready.

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So let's go through it once more.

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First the send command is invoked.

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Let's say it's to take off the response for the take off comes back.

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If there is no response the system will wait for it.

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If there is no response the loop will break.

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If the response does come back the value will be set to self response.

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Then the response OK will be decoded and set to be returned as we set the response to be return.

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We can rewrite the takeoff and land command to return as well.

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We finish cleaning the code so let's run the code again and see how the results come out.

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As I run the code you can see that the command and the response are paired from the top it's command

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okay stream on OK.

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The response to take off may take a bit of time but here you see the response come out as OK.

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Now the Land Command has been sent and the response comes back.

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OK here we've successfully programmed our drone with a very clean log.

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Great job.

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I'll see you in our next lesson.