1. A communication method comprising:counting a number of one or more communication terminals which stores data, for each piece of data, in accordance with each piece of data information, transmitted from each another communication terminal, indicating the each piece of data stored in the another communication terminal, and stored contents in a storage unit in the own terminal;
estimating a number of zero or more communication terminals mutually transmitting data at a same timing in accordance with the counting result;
calculating an adjustment reference value for limiting the estimated number of zero or more communication terminals to a preset permissible number or less;
determining whether or not to permit transmission of data stored in the storage unit in accordance with the calculated adjustment reference value; and
transmitting the data to a communication terminal not storing the data, when permitting transmission of the data.