WEBVTT 00:00.080 --> 00:04.850 In this lesson you will learn how to create a Cplusplus service server. 00:04.850 --> 00:08.420 We will do the exact same thing as we did for Python. 00:08.420 --> 00:12.500 So let's start very quickly with the interface we have used. 00:12.500 --> 00:24.650 So Ros2 interface show we have used the example interfaces and then save and then add two ints which 00:24.650 --> 00:28.160 contains a request that's a and b. 00:28.160 --> 00:29.660 So we have two fields. 00:29.690 --> 00:32.480 Each one is an int 64. 00:32.510 --> 00:36.860 Then three dashes to separate the request from the response. 00:36.860 --> 00:40.220 And then we have a some field in the response okay. 00:40.250 --> 00:45.200 So we have two different messages request and then response. 00:45.200 --> 00:50.480 And we are going to use this interface inside our service server and client. 00:50.480 --> 00:53.300 So let's create a node for the service server. 00:53.480 --> 01:01.790 We are going to our C plus plus package this time and in the source folder of that C plus plus package 01:01.790 --> 01:04.670 where we have all our CPP files. 01:04.670 --> 01:06.890 So let's create a new one. 01:06.890 --> 01:11.450 Let's call it add to int server dot cpp. 01:11.900 --> 01:14.450 And then we can open VSCode. 01:14.450 --> 01:20.810 I'm going to open it once again from the same place, which is the source folder of the roster workspace 01:20.810 --> 01:22.580 with code dot. 01:24.200 --> 01:27.230 Okay let's open that file. 01:28.880 --> 01:30.380 And I don't need that. 01:30.380 --> 01:32.540 And we can get the template. 01:33.080 --> 01:33.290 Okay. 01:33.290 --> 01:37.070 So I'm going to use the C plus plus template for nodes. 01:37.250 --> 01:38.420 Let's save. 01:38.420 --> 01:41.840 So we have the auto completion and the include is found. 01:41.870 --> 01:42.350 Okay. 01:42.380 --> 01:48.950 And let's rename that add to int server node. 01:49.790 --> 02:00.720 We replace it here and there and there we can also rename the node add to its server. 02:02.370 --> 02:03.240 Okay. 02:03.270 --> 02:04.980 Just like that. 02:05.520 --> 02:10.590 And then first things first, let's include the interface that we will need for the server. 02:10.650 --> 02:16.620 So include example interfaces slash. 02:16.620 --> 02:18.660 And you see now it's not going to be MSG. 02:18.690 --> 02:20.460 It's going to be S r v. 02:20.550 --> 02:24.720 And then add to hints dot http. 02:25.410 --> 02:25.740 All right. 02:25.770 --> 02:28.770 We import that one and let's save again. 02:28.770 --> 02:30.690 So that is going to be found. 02:30.720 --> 02:33.750 Now we can create our service server. 02:33.750 --> 02:37.770 And first we are going to declare it as a private attribute. 02:37.770 --> 02:40.590 So how to create a service server. 02:40.590 --> 02:42.030 You do Clcp. 02:42.750 --> 02:46.050 And then that's going to be service. 02:46.080 --> 02:52.380 You need to give the type here with a template, just like we did for publishers and subscribers. 02:52.380 --> 02:53.250 It's going to be the same. 02:53.250 --> 02:54.390 So what is the type. 02:54.390 --> 03:03.180 It's example interfaces solve and add to ints. 03:03.300 --> 03:04.770 Okay, I close the bracket. 03:04.770 --> 03:06.510 And actually that's not all. 03:06.510 --> 03:12.660 We are not just going to create a service, we are going to create a guess what a shared pointer to 03:12.690 --> 03:13.530 the service. 03:13.560 --> 03:13.830 Okay. 03:13.860 --> 03:19.740 So we use once again the shared PTR helper here for most things we have in rust. 03:19.740 --> 03:21.420 And let's name that server. 03:21.420 --> 03:23.520 So we have the declaration here. 03:23.520 --> 03:26.850 Let's initialize it in the constructor. 03:26.880 --> 03:31.080 Server is equal to and I'm using this. 03:32.190 --> 03:35.220 Okay no need but it's to make this explicit. 03:35.610 --> 03:38.670 Create service. 03:38.820 --> 03:39.030 Okay. 03:39.030 --> 03:44.820 So to create a service we use the create service we need to provide once again the interface. 03:44.850 --> 03:52.020 Example interfaces solve add to ints. 03:52.470 --> 03:53.010 All right. 03:53.010 --> 03:55.090 And then open and close the parentheses. 03:55.120 --> 03:56.110 Semicolon. 03:56.110 --> 03:57.880 And what do we need to provide. 03:57.880 --> 04:01.450 Well we've already provided the interface here. 04:01.450 --> 04:03.610 So now we need to provide the name. 04:03.610 --> 04:07.930 And the name is well we choose the name because we create the service here. 04:07.930 --> 04:09.160 We choose the name. 04:09.160 --> 04:14.590 Let's choose add to insert to make the same as what we did with Python. 04:14.590 --> 04:17.860 And then we need to provide a callback okay. 04:17.890 --> 04:20.020 So let's create the callback now. 04:20.020 --> 04:23.920 And the callback is simply because well once again you create a server. 04:23.950 --> 04:26.530 But the server is not going to do anything on its own. 04:26.530 --> 04:30.910 You need to send a request from the outside of this node to this server. 04:30.910 --> 04:34.480 And when you get a request, you need to be able to process it. 04:34.480 --> 04:41.380 And for that, we just create a callback so that when the node is spinning, we can execute that callback. 04:41.380 --> 04:47.350 And I'm going to add it here in private because we don't want to call this callback directly ourselves. 04:47.380 --> 04:50.680 It's going to be called by the spinning mechanism. 04:50.680 --> 04:52.060 And so that's going to be void. 04:52.100 --> 04:53.930 It's not going to return anything. 04:53.960 --> 04:55.790 Here is the difference with Python. 04:55.820 --> 05:01.490 In Python you had to return the response from the from the function from the callback. 05:01.520 --> 05:02.720 Here it's going to be void. 05:02.720 --> 05:04.550 So we don't return anything. 05:04.580 --> 05:09.170 Let's call it callback add to int. 05:09.470 --> 05:12.320 And here you will receive also two things. 05:12.320 --> 05:16.460 You will receive the request and the response. 05:16.460 --> 05:23.540 And actually you receive a const shared pointer of the request and a const shared pointer of the response. 05:23.570 --> 05:25.130 And so that's going to be const. 05:25.970 --> 05:35.960 Example interfaces solve add to ints and request okay. 05:35.990 --> 05:38.810 So you see we have the request message inside it. 05:38.840 --> 05:39.350 Twins. 05:39.380 --> 05:40.730 This is not a message. 05:40.730 --> 05:41.720 This is a combination. 05:41.720 --> 05:43.310 This is a pair of messages. 05:43.310 --> 05:48.200 And then we have shared pointer plus let's name it request. 05:48.200 --> 05:52.940 So you can see it's quite long but that's the full type you need to provide. 05:52.940 --> 05:54.170 We have the request. 05:54.170 --> 05:57.770 And then comma, I'm going to go back to a new line here. 05:57.890 --> 06:05.030 And let's do const example interfaces salve add to int. 06:05.060 --> 06:13.670 This one is going to be the response and also a shared pointer to the response response okay. 06:13.700 --> 06:19.280 And we can open and close the curly brackets for the method. 06:19.280 --> 06:23.240 So what do we do in this service callback. 06:23.240 --> 06:25.700 Well we are going to process the request. 06:25.730 --> 06:29.090 Maybe you need to validate some data or check stuff. 06:29.270 --> 06:34.670 Maybe you need to do an action like turn on an LED, activate a motor, etc.. 06:34.670 --> 06:37.670 Here we just want to return a sum. 06:37.670 --> 06:40.670 So the sum of the two elements we have in the request. 06:40.670 --> 06:42.620 So we are going to do response. 06:42.620 --> 06:56.690 And because this is a pointer we use an arrow response sum is equal to request a plus, request A row 06:56.720 --> 06:57.470 B. 06:58.550 --> 06:58.970 Okay. 06:59.000 --> 07:01.880 And that's basically it for this. 07:01.880 --> 07:03.470 You don't need to return anything. 07:03.470 --> 07:07.010 Now I'm also going to print a log here so we know what's happening. 07:07.220 --> 07:10.640 Club info with. 07:10.670 --> 07:14.900 So this get logger. 07:14.900 --> 07:16.190 And then. 07:16.190 --> 07:18.440 So we're going to have a integer. 07:18.440 --> 07:23.990 So that's percentage D plus integer is equal to integer. 07:23.990 --> 07:27.020 And I provide the three elements here. 07:27.020 --> 07:40.040 So just in case I'm going to cast it to an integer there's going to be request a and then int request 07:40.400 --> 07:50.270 b and then int response some which is already set, and a semicolon. 07:50.660 --> 07:53.360 And maybe let's just go back to a new line here. 07:54.740 --> 07:55.370 Okay. 07:55.370 --> 07:57.590 So that's it for the callback. 07:57.590 --> 08:00.500 Now we need to go back here to the constructor. 08:00.500 --> 08:06.860 So we come back to this create service where we have the the type the name. 08:06.860 --> 08:08.870 And we need to provide the callback. 08:08.870 --> 08:11.720 So I'm going to do that on a new line. 08:11.720 --> 08:14.870 And then this also on a new line. 08:15.230 --> 08:18.410 And we need to do STD bind okay. 08:18.440 --> 08:20.720 So for a callback you will use Stdbind. 08:20.750 --> 08:26.450 Once again the first thing is the reference to the function. 08:26.450 --> 08:31.580 So add two ints seven node that's the class name. 08:31.580 --> 08:34.670 And then callback add two ints. 08:34.670 --> 08:38.720 That's the name of the function here with no parentheses. 08:38.810 --> 08:44.210 Second argument in the stdbind is this to link to that object here. 08:44.210 --> 08:50.490 And then because we have two parameters, we need to place two placeholders. 08:50.490 --> 08:54.660 So placeholder one and placeholder two. 08:55.050 --> 09:04.050 Instead of doing STD placeholders one directly here I'm going to be using the namespace using namespace 09:04.470 --> 09:08.100 std placeholders. 09:08.310 --> 09:08.880 Okay. 09:08.910 --> 09:13.200 So I can just do underscore one and then underscore two. 09:13.230 --> 09:13.530 Okay. 09:13.560 --> 09:15.210 So we have two arguments. 09:15.360 --> 09:18.000 We use underscore one and then underscore two. 09:18.030 --> 09:21.600 So in the STD bind you have four parameters to provide. 09:21.630 --> 09:22.020 Okay. 09:22.050 --> 09:25.980 And let's finish this constructor with a log sleep. 09:27.000 --> 09:34.650 And for this get logger and service. 09:34.650 --> 09:42.330 So add to insert a service has been studied for example. 09:42.360 --> 09:44.580 All right let's do a quick recap here. 09:44.580 --> 09:47.040 So we're going to initialize roster communications. 09:47.040 --> 09:49.710 And then we create a shared pointer to the node. 09:49.710 --> 09:52.830 When we get to the constructor we create a server. 09:52.830 --> 09:58.230 And we're going to register that callback for the add to server. 09:58.260 --> 10:01.800 Then the node is going to spin and when the client. 10:01.800 --> 10:05.730 So when one client sends a request it's going to be processed. 10:05.730 --> 10:08.760 Inside this callback we receive the request. 10:08.790 --> 10:11.880 We also have the response object directly. 10:11.880 --> 10:13.860 And what we need to do is to fill. 10:13.890 --> 10:19.590 So to do an action and to fill the response object and that's it. 10:19.620 --> 10:26.310 After this function will exit, then the response is going to be sent back automatically to the client. 10:26.340 --> 10:26.730 All right. 10:26.730 --> 10:28.230 So let's save this file. 10:28.230 --> 10:34.290 And let's go to the Cmakelists.txt to build and install an executable. 10:35.250 --> 10:36.330 So let's do that here. 10:36.360 --> 10:38.310 Add executable. 10:38.790 --> 10:48.190 Add to INS severe from ad to int server dot cp. 10:48.430 --> 10:48.820 All right. 10:48.850 --> 10:50.110 That's the file here. 10:50.110 --> 10:52.390 I'm going a bit faster now because we've done already. 10:52.390 --> 10:52.960 You see that. 10:52.960 --> 11:01.810 We've done already that five times payment target dependencies with the executable name. 11:01.810 --> 11:06.880 And what do we need Lclc-rp and example interfaces. 11:06.910 --> 11:12.520 As you can see in the code we import the two packages and then we have the executable. 11:12.520 --> 11:16.480 I'm going to add it here add two int server. 11:16.510 --> 11:19.210 Now I can save and let's build that. 11:19.210 --> 11:25.570 So let's go back one directory and let's do a call on build packages. 11:25.570 --> 11:26.560 Select. 11:27.070 --> 11:31.000 And let's only build the my CPP package. 11:31.000 --> 11:33.550 So it's quite useful to use this packages select here. 11:33.550 --> 11:39.190 Because if you remember we had built the Python package with Simulink install. 11:39.190 --> 11:44.470 So if you build all the packages again without Simulink install, then you're going to lose the Simulink 11:44.470 --> 11:46.360 install option for the Python package. 11:46.360 --> 11:52.570 So that's why here we just build the Cplusplus one and we don't lose that benefit for the other packages. 11:52.600 --> 11:54.820 All right so I will just a quick parenthesis here. 11:54.820 --> 11:56.470 So let's build. 11:58.960 --> 12:03.910 And then let's solve the terminal or open new ones. 12:03.910 --> 12:12.940 And let's do a Ros to run my CPP package with add to in server okay. 12:12.970 --> 12:15.190 Add to in service has been started. 12:15.190 --> 12:16.690 I can do Ros two. 12:16.720 --> 12:18.880 Well I can do Ros two node list. 12:18.910 --> 12:29.350 Once again I find the node Ros two node info with that name in the service servers I see my add to int 12:29.350 --> 12:31.570 with the example interfaces. 12:31.690 --> 12:33.280 So we add to int. 12:33.310 --> 12:34.120 Great. 12:34.120 --> 12:41.180 And now what I could do is I could do Ros two service Call to test this service from the terminal. 12:41.420 --> 12:48.200 But if you remember, what we just did in the previous videos was to create a Python service client. 12:48.200 --> 12:52.100 So we already have a service client for that service and it's the same name. 12:52.100 --> 12:55.970 So why not just use the client that we already have. 12:56.000 --> 12:59.780 Let's do Ros to run my Python package. 12:59.780 --> 13:02.990 We've had two ints client. 13:02.990 --> 13:08.780 We can use the one with object oriented programming or the one with. 13:08.810 --> 13:11.210 So the script one with no op. 13:11.300 --> 13:13.340 And let's see if that works. 13:14.030 --> 13:15.770 And you can see it's working. 13:15.770 --> 13:20.780 So the Python client here sent a request that was processed by the server here. 13:20.780 --> 13:22.220 And we got the response. 13:22.220 --> 13:28.880 So you can see once again you can have a for example a Python client in one node and a C plus plus server 13:28.880 --> 13:29.630 in another node. 13:29.630 --> 13:30.650 And that's no problem. 13:30.650 --> 13:31.670 It's going to work the same. 13:31.670 --> 13:36.800 And with this we can also validate that our service server is correctly working.