Upload an audio file

Hello,

I would like to attach an audio file in a SOAP request.
I would like to place this file at a specific location in the request but I can't.
Here is the location in the request where I would like to drop the file:

<v1:mediamessage>
<xsd:codec>
<xsd:codecID>audio/MPA;layer=3</xsd:codecID>
</xsd:codec>
<xsd:location>Here the message.mp3 file i want to upload</xsd:location>
</v1:messageMedia>

I don't have a server installed on my pc.(XXX is because i prefer hide the ip)
If I do "attach" and select a file, I don't know where it will be placed in the request.
It seems to me that once the file is uploaded, I should have something like this instead:

<v1:messageMedia>
<xsd:codec>
<xsd:codecID>audio/MPA;layer=3</xsd:codecID>
</xsd:codec>
<xsd:location>cid:123564548786477</xsd:location>
</v1:messageMedia>

if I click on "attachment" and then select a file, when I select the drop-down list in the "part" column, the cid is not present either.

i've tried this method:

"

To specify a MTOM attachment:

1. Set the Enable MTOM request property to true.
2. Add a file to the Attachments tab as it was described above.
3. In the Part column, select the cid identifier that your request body specifies

"

I hope you will understand my request

thank you in advance for your help because I'm stuck here.