Image forming apparatus for establishing a connection with a terminal device using quick UDP internet connections (QUIC), terminal device for establishing a connection with an image forming apparatus using QUIC and control methods of those

1. An image-forming apparatus, comprising:

a controller;

a storage; and

a communicator, wherein

the controller

establishes a connection with a terminal device through the communicator using Quick UDP Internet Connections (QUIC),

stores, in the storage, identification information for identifying the connection and key information to be used for encryption of transmission-reception information transmitted and received to and from the terminal device,

performs communication of the transmission-reception information with the terminal device through Hypertext Transfer Protocol (HTTP)/3, and

establishes, when the connection with the terminal device is disconnected, a reconnection with the terminal device using the identification information and the key information, such that the communication of the transmission-reception information with the terminal device is resumed.

2. The image-forming apparatus according to claim 1 , wherein the key information is information on a common key used for communication using a TLS (Transport Layer Security) protocol.

3. The image-forming apparatus according to claim 1 , wherein the controller further

stores the identification information, the key information, and the transmission-reception information received from the terminal device that are associated with one another, and

resumes, when the communication with the terminal device is resumed, communication of the transmission-reception information that is associated with the identification information and the key information.

4. The image-forming apparatus according to claim 1 , wherein, when the connection with the terminal device is disconnected, the controller sets a period of time for accepting the reconnection from the terminal device, and the controller rejects a resumption of the communication of the transmission-reception information with the terminal device when the reconnection is attempted by the terminal device after the period of time has elapsed.

5. The image-forming apparatus according to claim 1 , wherein

the communicator communicates with a plurality of terminal devices including the terminal devices, and

the controller further establishes a connection with a second terminal device when a connection with a first terminal device is disconnected after the connection with the first terminal device is established, performs communication of transmission-reception information with the second terminal device, establishes a reconnection with the first terminal device after the connection with the second terminal device is disconnected, and performs communication of the transmission-reception information with the first terminal device.

6. The image-forming apparatus according to claim 5 , wherein, when the connection with the first terminal device is disconnected after the connection with the first terminal device is established and the communication of the transmission-reception information is performed after the connection with the second terminal device is established, and when the first terminal device requests establishment of the reconnection, the controller notifies the first terminal device of a usage of the image-forming apparatus by user.

7. A terminal device comprising:

a controller;

a storage; and

a communicator, wherein

the controller

establishes a connection with the image-forming apparatus through the communicator using Quick UDP Internet Connections (QUIC),

stores, in the storage, identification information for identifying the connection and key information to be used for encryption of transmission-reception information transmitted and received to and from the image-forming apparatus,

performs communication of the transmission-reception information with the image-forming apparatus through Hypertext Transfer Protocol (HTTP)/3, and performs, when the connection with the image-forming apparatus is disconnected, a

reconnection to the image-forming apparatus using the identification information and the key information so as to resume the communication of the transmission-reception information with the image-forming apparatus.

8. The terminal device according to claim 7 , wherein, when resuming the communication of the transmission-reception information with the image-forming apparatus, the controller performs control, such that a message based on a state of the image-forming apparatus is displayed.

9. A method for controlling an image-forming apparatus, the method comprising:

establishing a connection with a terminal device by using Quick UDP Internet Connections (QUIC);

storing identification information for identifying the connection and key information to be used for encryption of transmission-reception information transmitted and received to and from the terminal device;

performing communication of the transmission-reception information with the terminal device through Hypertext Transfer Protocol (HTTP)/3; and

establishing, when the connection with the terminal device is disconnected, a reconnection with the terminal device using the identification information and the key information, such that the communication of the transmission-reception information with the terminal device is resumed.

10. A method for controlling a terminal device, the method comprising:

establishing a connection with an image-forming apparatus using Quick UDP Internet Connections (QUIC);

storing identification information for identifying the connection and key information to be used for encryption of transmission-reception information transmitted and received to and from the image-forming apparatus;

performing communication of the transmission-reception information with the image-forming apparatus through Hypertext Transfer Protocol (HTTP)/3; and

performing, when the connection with the image-forming apparatus is disconnected, a reconnection to the image-forming apparatus using the identification information and the key information, such that the communication of the transmission-reception information with the image-forming apparatus is resumed.