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At this point, we just need to tell MQTT Transmission which folder contains the file(s) to sendpublish. Download and unzip this sample file to some location and note that location.

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Note

When transferring files using auto_publish, MQTT Transmission requires two files to be present before it will transfer the target file. The first is the file itself. The second is a file that has the same name as the target file followed by a '.md5' extension.   The file containing the md5 sum file is needed to ensure that the file to be transferred is complete and ready to be publishedof the target file will not be transferred.

The contents of that file must contain the Message Digest Algorithm 5 (or MD5 sum) of the file. The MD5 sum can be calculated using command line utilities on most operating systems or through scripting in Ignition. Here are some examples:

Linux

Code Block
languagebash
ubuntu@linux-host:~$ md5sum myfile.bin
07180622a24ebf905cf5f770cd54197a  myfile.bin

# In the above example, the md5 sum is: 07180622a24ebf905cf5f770cd54197a

OSX

Code Block
languagebash
user@osxhost:~$ md5 sample_file.txt
MD5 (sample_file.txt) = 85324ffbcc7d97c478adf53796aff787

# In the above example, the md5 sum is: 85324ffbcc7d97c478adf53796aff787

Windows

Code Block
languagepowershell
Get-FileHash -Algorithm MD5 .\some_file.iso

Algorithm       Hash                                                                   Path                                                                              
---------       ----                                                                   ----                                                                              
MD5             80FD169D3FDADBC97E66C168F796B1BF                                       C:\temp\some_file.iso

# In the above example, the md5 sum is: 80FD169D3FDADBC97E66C168F796B1BF

Ignition Script

Code Block
languagepy
import hashlib

# File to create md5 sum
file_name = "D:\MyFiles\test_file.txt"

# Open,close, read file and calculate MD5 on its contents 
with open(file_name, 'rb') as file_to_check:
    # read contents of the file
    data = file_to_check.read()    
    # pipe contents of the file through
    md5_returned = hashlib.md5(data).hexdigest()
    
# Save md5 sum file
f = open(file_name + ".md5", "w")
f.write(md5_returned)
f.close()


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