# COAP response changing HEX buffer
**URL:** https://discourse.nodered.org/t/coap-response-changing-hex-buffer/78443
**Category:** General
**Created:** [15 May 2023 18:01 UTC](https://discourse.nodered.org/t/coap-response-changing-hex-buffer/78443 "2023-05-15T18:01:16Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@JohnnyPicnic](https://discourse.nodered.org/u/JohnnyPicnic)
#### Post date: [15 May 2023 18:01 UTC](https://discourse.nodered.org/t/coap-response-changing-hex-buffer/78443/1 "2023-05-15T18:01:16Z")
Hi All, I'm tying to respond to a COAP request with a buffer of:
```auto
[64,219,228,137,163,6]
```
```auto
String: 4090e589a306
```
The COAP response is coming out as:
```auto
[64,239,191,189,229,137,163,6]
```
```auto
String: 40efbfbde589a306
```
I've tried different encoding formats and using the buffer maker but can't seem to figure out why it's changing.
---
### Author:  [@JohnnyPicnic](https://discourse.nodered.org/u/JohnnyPicnic)
#### Post date: [15 May 2023 18:52 UTC](https://discourse.nodered.org/t/coap-response-changing-hex-buffer/78443/2 "2023-05-15T18:52:02Z")
Some more info:
If I set the response payload to `12345678`
the request response comes out as `3132333435363738`
or buffer
```auto
[49,50,51,52,53,54,55,56]
```
---
### Author:  [@JohnnyPicnic](https://discourse.nodered.org/u/JohnnyPicnic)
#### Post date: [17 May 2023 12:54 UTC](https://discourse.nodered.org/t/coap-response-changing-hex-buffer/78443/3 "2023-05-17T12:54:17Z")
I ended up finding an issue in node-red-contrib-coap where the content format is being set to one of three options and none of them allow just an unchanged payload to pass through.
My quick and dirty fix was to set text/plain to msg.payload
```auto
if (_checkContentFormat(contentFormat, "text/plain")) {
return msg.payload.toString();
} else if (_checkContentFormat(contentFormat, "json")) {
return JSON.stringify(msg.payload);
} else if (_checkContentFormat(contentFormat, "cbor")) {
return cbor.encode(msg.payload);
} else {
return msg.payload.toString();
}
```
---
### Author:  [@system](https://discourse.nodered.org/u/system)
#### Post date: [31 May 2023 12:55 UTC](https://discourse.nodered.org/t/coap-response-changing-hex-buffer/78443/4 "2023-05-31T12:55:09Z")
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