In computer networking, Server Message Block (SMB) operates as an application-level network protocol mainly used to provide shared access to files, printers, serial ports, and miscellaneous communications between nodes on a network. It also provides an authenticated Inter-process communication mechanism. Most usage of SMB involves computers running Microsoft Windows, where it is often known simply as "Microsoft Windows Network".
Samba, which re-implements the SMB protocol and the Microsoft extensions to it as free software, includes an SMB server and a command-line SMB client.
Exploring the SMB2 protocol
OpenSolaris Project: CIFS Server