A detecting method is provided, which includes extracting an Internet Protocol Identifier value from an obtained data packet. The detecting method may further include searching in a record table containing a correspondence relationship between an Internet Protocol Identifier value and a terminal serial number to determine whether the record table contains an adjacent Internet Protocol Identifier value smaller than the extracted Internet Protocol Identifier value and modifying the adjacent Internet Protocol Identifier value that is smaller than the extracted Internet Protocol Identifier value to be the extracted Internet Protocol Identifier value if the record table contains the adjacent Internet Protocol Identifier value smaller than the extracted Internet Protocol Identifier value. Otherwise, the detecting method may also include, adding a new record of the extracted Internet Protocol Identifier value and the corresponding terminal serial number into the record table. When a notification is received, the detecting method may calculate the number of terminal serial numbers in the record table and output the number of terminal serial numbers as the number of hosts. The provided detecting method may further provide a corresponding statistic and analyzing server and a detecting system.