Method for establishing communication within a closed network

A method for establishing communication within a closed network, the method being implemented using a first closed server cooperatively with a public server, the first closed server being in communication with the public server and being installed with a first instant messaging service system exclusive to a first group of people, the first instant messaging service system including a first communication group that includes at least one first inside party within the first group of people, the method comprising:

• receiving, by the first closed server, identification information associated with a first outside party not belonging to the first group of people from a first staff-end device that is in communication with the first closed server and that is associated with the first inside party;
• transmitting, by the first closed server, link information to a first outside party device that is associated with the first outside party via the public server, the link information including a link for downloading an instant messaging application;
• in response to receipt of a registration request from the first outside party device executing the instant messaging application, transmitting, by the public server, an identifier associated with the first communication group to the first outside party device;
• and
• in response to receipt of the identifier from the first outside party device executing the instant messaging application, by the first closed server, adding the first outside party to the first communication group and enabling the first outside party to communicate exclusively with the first inside party via the first instant messaging service system.