Example usage of HTTPLib_POST (HTTPLib)

[KrzysztofSoczewka]

I'm using HTTPLib_POST (HTTPLib library, embedded target) to send a JSON body to an external HTTP API.

Looking at the inputs, reqHeaders (STRING[2047]) accepts headers directly as a string, but there's no direct string input for the body – only srcFilename ("Source filename to be posted as body"). So the only way seems to be:

1. Write the JSON to a file first (e.g. HTTPLib_SaveBinaryFile)
2. Pass that filename via srcFilename in HTTPLib_POST
3. Read responseStatusCode / responseBody once done is TRUE

This works for me, but I'd like to confirm:

• Is file-based body really the only intended method, or is there a variant/way to pass the body as a string directly?
• Is there an official example project showing HTTPLib_POST with a JSON body?

Any pointers would be appreciated. Thanks!

[MargheritaM]

Hello, 
unfortunatelly there isn't a way to pass the body with a STRING, you have to use a file which results more flexible in terms of dimensions. 
Regarding an example project, we are working on an example showing how to use HTTP GET, POST, DELETE and PATCH. It will be released in the following weeks. 
Margherita

[KrzysztofSoczewka]

It's my code

count := count + 1;

IF count = 100 THEN
Start := TRUE;
count := 0;
END_IF;

epochSec := GetEpochTime_s();

refresh_post(enable := TRUE, period := period1);
trigEdge(clk := refresh_post.out);

IF trigEdge.q AND seq = 0 THEN
deleteResult := HTTPLib_DeleteFile(filename := bodyFile);

url1 := 'https://logs-prod-043.grafana.net/loki/api/v1/push';
reqHeaders1 := 'Authorization: Basic MTY2NzI2OTpnbxxxxxxxx';
reqHeaders1 := CONCAT(reqHeaders1, '$R$N');
reqHeaders1 := CONCAT(reqHeaders1, 'Content-Type: application/json');

jsonBody := '{"streams":[{"stream":{"job":"plc","device":"PLC1"},"values":[["';

epochStr := TO_STRING(epochSec);
epochStr := CONCAT(epochStr, '000000000');
jsonBody := CONCAT(jsonBody, epochStr);

jsonBody := CONCAT(jsonBody, '","temperatura=');

valStr := TO_STRING(v08740);
jsonBody := CONCAT(jsonBody, valStr);

jsonBody := CONCAT(jsonBody, '"]]}]}');

saveResult := HTTPLib_SaveBinaryFile(
filename := bodyFile,
inBuff := ADR(jsonBody),
buffSize := LEN(jsonBody)
);

IF saveResult = 0 THEN
enablePost := TRUE;
seq := 1;
END_IF;
END_IF;
//

post1(
enable := enablePost,
url := url1,
srcFilename := '/SD/loki_body.json',
reqHeaders := reqHeaders1,
tls := TRUE,
allowIfServerNotVerified := FALSE
);

postTimeout(in := (seq = 1), pt := 5000);

IF post1.done OR postTimeout.q THEN
IF post1.done THEN
statusCode := post1.responseStatusCode;
responseBody := post1.responseBody;
END_IF;
enablePost := FALSE;
seq := 0;
postTimeout(in := FALSE); // reset timera
END_IF;

Start := FALSE;

I think the problem may be caused by an incorrect file path: srcFilename := '/SD/loki_body.json';. What path should be used?

[williamFolle · Accepted solution]

Hello, yes, I can confirm that you only need to specify the name of the document you created.

In your case, 

srcFilename := 'loki_body.json';

should be enough to make everything work.

[FedericoM]

The http functions working on files use a private internal filesystem, filename is enough