Experimental HTTP Client for NX/NJ

This is an experimental implementation of HTTP/1.1 client for OMRON's NX/NJ controllers. This HTTP client lacks functionality and is not of sufficient quality. However, it shows that it is possible to implement a practical HTTP client with a user program using Sysmac Studio and the NX/NJ controller. The Sysmac project contains several test programs that actually query Beeceptor's HTTP echo server. For details, please check this article (Japanese).

The HTTP client has the following restrictions.

• Can't use proxy
• Invalid responses can cause tasks to time out

Inquiries using HTTP(S) can be written as follows.

    // POST /chat/api/v1 ContentType: application/json
    20:
        IF NewHttpClientTask(
               Context:=iHttpContext,
               ClientTask:=iHttpClientTask)
        THEN
            HttpPost(Context:=iHttpContext,
                     Url:='https://echo.free.beeceptor.com/chat/api/v1',
                     KeepAlive:=FALSE,
                     ClientTask:=iHttpClientTask);
            SetHttpHeader(Context:=iHttpContext,
                          Key:='X-Api-Key',
                          Value:='xxxxxx');
            SetContentStr(
                Context:=iHttpContext,
                ContentType:='application/json',
                Content:='{"channel":"hell","name":"taker","msg":"Have you played Awaria?"}');
            iPostTick := 0;
            InvokeHttpClientTask(Context:=iHttpContext,
                                 ClientTask:=iHttpClientTask);
            
            Inc(iState);
        END_IF;
    21:
        CASE HttpClientTaskState(Context:=iHttpContext,
                                 ClientTask:=iHttpClientTask) OF
            HTTP_CLIENT_TASK_STATE_CLOSED:
                iState := iTransState;
            HTTP_CLIENT_TASK_STATE_RESPOND:
                CASE GetStatusCode(Context:=iHttpContext) OF
                    200: // OK
                        iPostRspContentType
                            := GetContentType(Context:=iHttpContext); 
                        GetContent(Context:=iHttpContext,
                                   Out:=iRspBinBody,
                                   Head:=0,
                                   Size=>iRspBinBodySize);
                        iPostRspContent
                            := AryToString(In:=iRspBinBody[0],
                                           Size:=iRspBinBodySize);
                        
                        iState := iTransState;
                    204: // No Content
                        iState := iTransState;
                ELSE
                    Inc(iState);
                END_CASE;
            HTTP_CLIENT_TASK_STATE_REQUESTING:
                Inc(iPostTick);
            HTTP_CLIENT_TASK_STATE_ERROR:
                GetHttpClientError(Context:=iHttpContext,
                                   Error=>iError,
                                   ErrorID=>iErrorID,
                                   ErrorIDEx=>iErrorIDEx);
                iState := iState + 7;
        END_CASE;

Usage environment

The following environment is required to use this project

Controller	NX1 or NX5
Sysmac Studio	I always recommend the latest version.
Network	Must be able to connect to the Internet.

Built environment

This project was built in the following environment.

Controller	NX102-9000 Ver 1.64
Sysmac Studio	Ver.1.61

Test program usage steps

The Sysmac project includes a test program (Test_HttpEcho) that queries Beeceptor's HTTP echo server. There may be some restrictions when accessing from a network that is not under your control. If possible, use a test network to ensure there are no constraints.

1. Change controller settings

Set the controller model of this project to match the controller model to be used, and to enable Internet connection and name resolution. At least the gateway and DNS server settings are required.

2. Change controller to program mode

Set the controller to program mode to prevent unintended operation and to configure secure sockets.

3. Transfer Sysmac project to controller

Keep the controller in program mode to prevent the program from running.

4. Register TLS session in secure socket settings

Register a TLS session with zero ID and no client certificate. Do the following while online to the controller.

5. Register variables in Watch window

Paste the following into Watch window.

LIB	Test_HttpEcho.iGetRspContent
LIB	Test_HttpEcho.iPostRspContent
LIB	Test_HttpEcho.iPostFormRspContent
LIB	Test_HttpEcho.iPutRspContent
LIB	Test_HttpEcho.iPatchRspContent
LIB	Test_HttpEcho.iDeleteRspContent

6. Change controller to operation mode

The moment you switch to driving mode, it starts making requests to the server.

7. Check Watch window

If there is a response from the server, the HTTP response will be displayed as shown below.

If an error occurs, there are the following possibilities:

• Incorrect secure socket settings
  Check if the ID is zero.
• HTTP echo server is down
  Ping the HTTP echo server from your device and check the response.
• Not connected to the Internet or unable to resolve name
  Check the route to the HTTP echo server with tracert.