This action allows you to save a portion of the received binary to a file, appending to the file if it already exists.

It takes three parameters:

  1. The position in the received binary to be the first byte added to the file.
    Position 0 is the start of the message.
  2. From parameter 1's position, how many bytes that you want to append to the file.
    You can use the Received binary > Get binary size expression to append the whole received message.
  3. The file path to save to.
    You can press the expression button on bottom right of the dialog to use an evaluated path instead.
    Only Lacewing Blue is capable of writing to long file paths (more than 255 characters) or using Unicode characters in paths.


At the end of the action, the binary message range indicated by your passed position/number of bytes expressions will be added to the end of the file. If the file didn't exist, it will be created with the range as its content.


Using a filename received from a client/server message is unsafe. To use filenames safely, read Security > Safe filenames section.