I am trying to send a document by converting it into base64 string. The api requires content-length as a require header input. While trying the callout using postman, I am able to make a successful callout as postman calculates the content-length on runtime. But if i change the value to a manual input[any value]. It gives me a read-timout in salesforce/ postman.
Any help would be really appreciated.
Regards, Ankit
Sounds like you're trying to send a DocuSign envelope (signing request) by using Apex.
This Apex example shows you how to send an envelope including the addition of a document.
I suggest that you get this example running on your system, then ask a new question in StackOverflow if needed.
This question could have (should) include much more detail on what you were trying and what didn't work.