^start of line
\S+any non-whitespace character, repeated at least once
\s+any whitespace character, repeated at least once
\d{4}a digit, repeated exactly 4 times
\*the literal * (4210 / 528 / 2A16)
Group session_id(?<session_id>[^\*]+) Negated Character Class[^\*]+ +matches at least one character outside the set below:
\*the literal * (4210 / 528 / 2A16)
\*the literal * (4210 / 528 / 2A16)
g modifier: global. Finds all matches instead of stopping after the first
m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string