Server, data cache method, communication system and communication method using server

PROBLEM TO BE SOLVED: To improve cache efficiency of a transmission node.SOLUTION: A server includes: a storage part for storing an original file and characteristics of the original file; an encoding part for generating an encoded symbol by encoding the original file stored in the storage part; an information acquisition part for communicating with at least one transmission node and acquiring state information from the at least one transmission node; a control part for calculating the number of encoded symbols to be transmitted to the at least one transmission node and cached on the basis of the characteristics of the original file stored in the storage part and the state information of the at least one transmission node acquired by the information acquisition part; and a communication part for transmitting the encoded symbol to the at least one transmission node on the basis of the number of the encoded symbols calculated by the control part.