A message exchange method performed in a system including a plurality of access points that transmit annunciation signals including their addresses, a portable terminal that can be connected to a wide area network and receives the annunciation signals transmitted from the access points, and a message server that is connected to the wide area network and stores a message table including the addresses of the plurality of access points and a plurality of messages the method comprising: in order for the portable terminal to acquire at least one message from the message server, a first step of allowing the portable terminal to search for access points in a vicinity of the portable terminal and to receive the annunciation signal including the address of the access point from each of searched access points; characterized in that the message table includes a plurality of sets of the addresses of the access points, wherein each set of the addresses is associated with one of the plurality of messages, the method further comprising: a second step of allowing the portable terminal to transmit, to the message server, a message acquisition request which includes, as a query, a set of the addresses of the searched access points included in the annunciation signals; a third step of allowing the message server to compare the set of the addresses as the query which is included in the message acquisition request with each of the plurality of sets of addresses recorded in the message table to determine a similarity between the set of the addresses as the query and each of the plurality of the sets of addresses recorded in the message table and to extract one or more messages from the plurality of messages in the message table corresponding to one or more sets of the addresses in the message table which rank high among the plurality of sets of the addresses in the message table that are arranged in descending order of the similarities; and a fourth step of allowing the message server to transmit the one or more extracted messages as a response to the portable terminal. in order for the portable terminal to acquire at least one message from the message server, a first step of allowing the portable terminal to search for access points in a vicinity of the portable terminal and to receive the annunciation signal including the address of the access point from each of searched access points; characterized in that the message table includes a plurality of sets of the addresses of the access points, wherein each set of the addresses is associated with one of the plurality of messages, the method further comprising: a second step of allowing the portable terminal to transmit, to the message server, a message acquisition request which includes, as a query, a set of the addresses of the searched access points included in the annunciation signals; a third step of allowing the message server to compare the set of the addresses as the query which is included in the message acquisition request with each of the plurality of sets of addresses recorded in the message table to determine a similarity between the set of the addresses as the query and each of the plurality of the sets of addresses recorded in the message table and to extract one or more messages from the plurality of messages in the message table corresponding to one or more sets of the addresses in the message table which rank high among the plurality of sets of the addresses in the message table that are arranged in descending order of the similarities; and a fourth step of allowing the message server to transmit the one or more extracted messages as a response to the portable terminal. a second step of allowing the portable terminal to transmit, to the message server, a message acquisition request which includes, as a query, a set of the addresses of the searched access points included in the annunciation signals; a third step of allowing the message server to compare the set of the addresses as the query which is included in the message acquisition request with each of the plurality of sets of addresses recorded in the message table to determine a similarity between the set of the addresses as the query and each of the plurality of the sets of addresses recorded in the message table and to extract one or more messages from the plurality of messages in the message table corresponding to one or more sets of the addresses in the message table which rank high among the plurality of sets of the addresses in the message table that are arranged in descending order of the similarities; and a fourth step of allowing the message server to transmit the one or more extracted messages as a response to the portable terminal.