A method for connecting one or more printers (100, 101, 102) with one or more participant clients entering a chat room hosted by a server, comprising: (a) at the server, creating a chat room in response to a request of a chief client, creating a two-dimensional code including link information to enter the chat room, a password to enter the chat room, and information about time when the two-dimensional code is created, transmitting the two-dimensional code to the chief client, and receiving from the chief client information related to one or more printers (100, 101, 102); (b) at the chief client, transmitting the two-dimensional code to the one or more printers (100, 101, 102),; at the one or more printers (100, 101, 102), printing the two-dimensional code on a repositionable note; at the one or more participant clients, photographing the two-dimensional code, obtaining from the photographed two-dimensional code link information to enter the chat room and the password to enter the chat room, transmitting to the server the obtained link information and the obtained password to make a request for approval to enter the chat room; and (c) at the server, allowing the one or more participant clients that have made a request for approval to enter the chat room using the link information obtained from the photographed image of the two-dimensional code to enter the chat room; and (d) at the server, transmitting information about the one or more printers linked to the chief client in the chat room and information to link to the one or more printers (100, 101, 102) to the one or more participant clients in order for the one or more participant clients to perform an automatic link to the one or more printers (100, 101, 102), wherein in the process (d), if the one or more participant clients are allowed to enter by the server, the one or more participant clients enter the chat room, and the one or more participant clients receive the information about the one or more printers (100, 101, 102), the information to link to the one or more printers (100, 101, 102), and a public key corresponding to secret keys stored in the respective one or more printers (100, 101, 102) from the server in the chat room, and the one or more participant clients use the received information to perform an automatic link to the one or more printers (100, 101, 102), (f) if the one or more participant clients transmit one or more images encrypted by using the public key to one of the one or more printers (100, 101, 102), the one of the one or more printers (100, 101, 102) decrypt the one or more images and print the decrypted one or more images on a repositionable note, and the information to link to the one or more printers (100, 101, 102) includes Bluetooth search names of the one or more printers (100, 101, 102) linked to the chief client and passwords to perform pairing. (a) at the server, creating a chat room in response to a request of a chief client, creating a two-dimensional code including link information to enter the chat room, a password to enter the chat room, and information about time when the two-dimensional code is created, transmitting the two-dimensional code to the chief client, and receiving from the chief client information related to one or more printers (100, 101, 102); (b) at the chief client, transmitting the two-dimensional code to the one or more printers (100, 101, 102),; at the one or more printers (100, 101, 102), printing the two-dimensional code on a repositionable note; at the one or more participant clients, photographing the two-dimensional code, obtaining from the photographed two-dimensional code link information to enter the chat room and the password to enter the chat room, transmitting to the server the obtained link information and the obtained password to make a request for approval to enter the chat room; and (c) at the server, allowing the one or more participant clients that have made a request for approval to enter the chat room using the link information obtained from the photographed image of the two-dimensional code to enter the chat room; and (d) at the server, transmitting information about the one or more printers linked to the chief client in the chat room and information to link to the one or more printers (100, 101, 102) to the one or more participant clients in order for the one or more participant clients to perform an automatic link to the one or more printers (100, 101, 102), wherein in the process (d), if the one or more participant clients are allowed to enter by the server, the one or more participant clients enter the chat room, and the one or more participant clients receive the information about the one or more printers (100, 101, 102), the information to link to the one or more printers (100, 101, 102), and a public key corresponding to secret keys stored in the respective one or more printers (100, 101, 102) from the server in the chat room, and the one or more participant clients use the received information to perform an automatic link to the one or more printers (100, 101, 102), (f) if the one or more participant clients transmit one or more images encrypted by using the public key to one of the one or more printers (100, 101, 102), the one of the one or more printers (100, 101, 102) decrypt the one or more images and print the decrypted one or more images on a repositionable note, and the information to link to the one or more printers (100, 101, 102) includes Bluetooth search names of the one or more printers (100, 101, 102) linked to the chief client and passwords to perform pairing.