# Error with httpClient

**URL:** <https://forum.inductiveautomation.com/t/error-with-httpclient/110295>\
**Category:** General Discussion\
**Created:** [August 30, 2025, 10:54pm UTC](https://forum.inductiveautomation.com/t/error-with-httpclient/110295 "2025-08-30T22:54:56Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![nabila](https://avatars.discourse-cdn.com/v4/letter/n/43a26b/32.png) [@nabila](https://forum.inductiveautomation.com/u/nabila)\
**Post date:** [August 30, 2025, 10:54pm UTC](https://forum.inductiveautomation.com/t/error-with-httpclient/110295/1 "2025-08-30T22:54:56Z")

</div>

below calls

- First one using old method `httpPost` and got replay Ok-200
- Second one using `httpClient.post` getting error below

`Status: 422`  
`Body: {"detail":[{"type":"missing","loc":["body"],"msg":"Field required","input":null}]}`

```python
### Working Fine ####

import system, json

####Blow one working fine 
url = "http://localhost:8001/getdata"
payload = {"message": "ping from httpPost"}

body = system.util.jsonEncode(payload)
headers = "application/json; charset=utf-8"

resp_text = system.net.httpPost(url, headers, body)
print "httpPost ->", resp_text

########## getting error 422######### 

import system, json

url = "http://localhost:8001/getdata"
payload = {"message": "ping from httpClient"}

client = system.net.httpClient()
body_bytes = bytearray(json.dumps(payload), "utf-8")

resp = client.post(
    url,
    headers={"Content-Type": "application/json; charset=utf-8",
             "Accept": "application/json"},
    data=body_bytes
)

print "Status:", resp.getStatusCode()
print "Body:", resp.getText()

```

---

<div class="post-metadata">

**Author:** ![ryan.white](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/ryan.white/32/73193_2.png) [@ryan.white](https://forum.inductiveautomation.com/u/ryan.white)\
**Post date:** [August 30, 2025, 11:09pm UTC](https://forum.inductiveautomation.com/t/error-with-httpclient/110295/2 "2025-08-30T23:09:47Z")

</div>

To start with, do not `import system`, `system.*` functions are available by default in all contexts (with some omitted dependent on scope). Second, unless you are doing something really out there with json, just use `system.util.jsonDecode/jsonEncode` instead of importing a python library. You did this with the first script but not the second?

You are specifying a content type of `application/json` but then passing a byte array, which normally would get a content type of `application/octet-stream`

Quoting the [manual](https://www.docs.inductiveautomation.com/docs/8.1/appendix/scripting-functions/system-net/system-net-httpClient#parameters-1):

> Data to send in the request. Defaults to None. [optional]  
> String data will be sent with a Content-Type of `text/plain; charset=UTF-8`, unless a different Content-Type header was specified.  
> Dictionaries will be automatically encoded into JSON to send to the target server, with a Content-Type header set to `application/json;charset=UTF-8` unless a different Content-Type header was specified.  
> Byte arrays will be streamed directly to the target server, with a Content-Type header of `application/octet-stream` unless a different Content-Type header was specified.

Based on your two scripts, you aren't actually doing a one to one comparison. The first script is only encoding the body data as a JSON object, the second is encoding as a byte array. Based on the manual, you should be able to pass the `payload` dictionary directly to the `data` parameter with no other encoding necessary.

Try using the following for your second script instead:

```python
resp = client.post(
    url,
    headers={"Content-Type": "application/json; charset=utf-8",
             "Accept": "application/json"},
    data=payload
)

```

---

<div class="post-metadata">

**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\
**Post date:** [August 30, 2025, 11:17pm UTC](https://forum.inductiveautomation.com/t/error-with-httpclient/110295/3 "2025-08-30T23:17:45Z")

</div>

Also, you are creating an `httpClient()` object on every event. This is extremely non-optimal. Create the client object in a project library script, outside any function, so it will be cached and re-used.

Some general Ignition scripting optimizations:

- Do not use the `import` statement directly in any event, nor in any `def` at all. Place all necessary imports in the outer level of a project library script, and create functions in that script to use the imported names.

- in events and transforms, use a one-line callout to a project library function, passing all context variables are function arguments. Do not write general logic in events.

- Use the right click menu on tabs in the project library script editor to "float" them, so you can edit library scripts while working anywhere else in the designer.

- In jython, `bytearray()` doesn't create a byte array that is acceptable to java. (It is effectively useless/wrong in jython, always.)

---

<div class="post-metadata">

**Author:** ![nabila](https://avatars.discourse-cdn.com/v4/letter/n/43a26b/32.png) [@nabila](https://forum.inductiveautomation.com/u/nabila)\
**Post date:** [August 30, 2025, 11:28pm UTC](https://forum.inductiveautomation.com/t/error-with-httpclient/110295/4 "2025-08-30T23:28:32Z")

</div>

Thanks a lot ryan and @pturmel for your guidance ,

issue solved it seems the endpoint using HTTP\_ 1\_1

```python
client = system.net.httpClient(version="HTTP_1_1")

```