A center server for communicating with a navigation device and multiple user terminals via a communication network, the center server comprising: a positional information storage for storing information indicating a current position of the navigation device, a symbol information storage for storing a symbol having the meaning of destination point, a map database for storing positional information of points, in association with character strings indicating the points, a destination point information storage for storing positional information of points associated to character strings together with the character strings being associated, in ascending order of distance from the current position of the navigation device, a positional information updater for updating the information in the positional information storage, to information indicating the current position of the navigation device being received, upon receipt from the navigation device, of the information indicating the current position thereof, a chat service part for managing an ID of a user logging in a chat, and upon receipt of a message from a user terminal used by the user logging in the chat, transmitting the message being received to all of the user terminals of the users logging in the chat, a symbol processor for extracting from the map database, the positional information of the point associated with the character string designated by the symbol in the message, when the symbol having the meaning of destination point exists in the message that the chat service part received from the user terminal, and a destination point information updater for additionally storing in the destination point information storage the character string and positional information of said point extracted by the symbol processor, the destination point information updater arranged to sort character strings in the destination point information storage in ascending order of distance of the associated positional information from the current position of the navigation device, and further arranged to transmit to all of the user terminals of the users logging in the chat the character strings being sorted, respectively in association with numbers in ascending order of distance from the current position of the navigation device. a positional information storage for storing information indicating a current position of the navigation device, a symbol information storage for storing a symbol having the meaning of destination point, a map database for storing positional information of points, in association with character strings indicating the points, a destination point information storage for storing positional information of points associated to character strings together with the character strings being associated, in ascending order of distance from the current position of the navigation device, a positional information updater for updating the information in the positional information storage, to information indicating the current position of the navigation device being received, upon receipt from the navigation device, of the information indicating the current position thereof, a chat service part for managing an ID of a user logging in a chat, and upon receipt of a message from a user terminal used by the user logging in the chat, transmitting the message being received to all of the user terminals of the users logging in the chat, a symbol processor for extracting from the map database, the positional information of the point associated with the character string designated by the symbol in the message, when the symbol having the meaning of destination point exists in the message that the chat service part received from the user terminal, and a destination point information updater for additionally storing in the destination point information storage the character string and positional information of said point extracted by the symbol processor, the destination point information updater arranged to sort character strings in the destination point information storage in ascending order of distance of the associated positional information from the current position of the navigation device, and further arranged to transmit to all of the user terminals of the users logging in the chat the character strings being sorted, respectively in association with numbers in ascending order of distance from the current position of the navigation device.