Sending UDP message with backslash

[chris3]

Hello,

I'm trying to send the following UDP message in Node-Red:

\apple

But the UDP message being received by the server is:

\\apple

I've been pulling my hair out for a couple of hours trying to come up with a fix and am still struggling. Could anyone help with a solution to this?

Chris

[cymplecy]

just tried a simple test sending to/from same machine and that seems to work OK

Does a simple local test work for you?

[chris3]

Hi cymplecy,

This is the same behaviour as I get in the node-red gui. But when I recieve the packet in PacketSender an additional backslash has been added (screenshots below).

I have, however come up with a solution in that I am using a function to generate the message in hex and then send it in hex. This has solved my problem and is giving the desired result:

var hexString = "5C6170706C65"; // Hexadecimal string to send
var buffer = Buffer.from(hexString, 'hex');
msg.payload = buffer;
return msg;

Chris

[Colin]

If you look at the Hex display in your screenshot you will see that the second \ does not actually exist. My guess is that it is being escaped on the display. What does that display look like when you send it as hex?

[chris3]

Well spotted!! I hadn't noticed that.

I'm sending the string as hex now and the ascii is displaying correctly with just the single backslash.

Chris

[Colin]

Interesting, and confusing.

[dceejay]

If you use the inject node to inject a string then it will escape the \ by adding another \ so \apple becomes \\apple - same as if you try to send hello\n to add a carriage return it will send hello\\n as a string... and not with a carriage return character that you want.

You can get round this by setting it to send Json (J) mode instead of String mode - as then "\apple" (now you have to add quotes as well to make it valid JSON) - will then get sent correctly