P1=1432263465 is unix time. 1432263465 = 22.05.2015 - 04:57:45. That was the easy part. But what p4 means, good question. The only constant here seems to be the %3d at the end.
P4 is the session key issued from WU Servers encoded in base64, which provides access to desired file associated with it. WU Servers verify both P4 and datetime parameter1 (P1) in their session table. If matched, you can download the file, otherwise not. Guess you know already the session is time-limited. I believe the P2 and P3 are 'Mode' and 'Cmd'.
As it was said before, you don't just "find" a download. The ESD URLs are parameter-tied to a specific ID and timeframe, you can't just generate a URL.