I want to know on the windows operating system, what is the port number for the file sharing service?For example as you know the port number for HTTP service is 80. So I need to know the port number of file sharing protocol?
I've seen all of these..file sharing related
UDP-137, UDP-138, TCP-139,TCP-445
And possibly TCP port 135, though that may be something to do with something called "RPC". 
on an windows 7 machine all of those are listening. Some are related to NETBIOS so you can do
This site http://ntsecurity.nu/papers/port445/
If the server has NBT enabled, it listens on UDP ports 137, 138, and on TCP ports 139, 445. If it has NBT disabled, it listens on TCP port 445 only.
And this site http://www.petri.co.il/whats_port_445_in_w2k_xp_2003.htm mentions
"In Windows 2000/XP/2003, Microsoft added the possibility to run SMB directly over TCP/IP, without the extra layer of NetBT. For this they use TCP port 445. "
So in 2K,XP,2003...and I suppose Win 7,8, it is possible to run file sharing on only port 445 But you'd be doing
start...\\ip rather than
If file transfer is via FTP - TCP/21, in case of SFTP - TCP/22