A communication system includes: communication terminals; and a server that can connect to and communicate with the communication terminals, wherein: the server including: a first communication section that communicates with the communication terminals; a storage section that stores a plurality of connection patterns each of which indicates timings at which the communication terminal will access the server; a pattern selection section that selects one of the connection patterns from the storage section; and a first control section that controls the first communication section to transmit the connection pattern selected by the pattern selection section to the communication terminal the first communication section connects to; and the communication terminal including: a second communication section that communicates with the server; and a second control section that controls the second communication section to connect to the server at timing indicated in the connection pattern received by the second communication section.