IoT device connected to server via NAT, and IoT communication method

An Internet of things (IoT) device connected with a server via a network address translation (NAT), the IoT device comprising:

• a communication unit configured to connect to the server via the NAT;
• and
• a controller configured to execute a first session for service connection,
• when the communication unit connects to a new network, identify whether a specific keep alive value corresponding to a corresponding network environment is stored in the server,
• when the specific keep alive value is stored, set the communication unit to communicate with the corresponding specific keep alive value, and
• when the specific keep alive value is not stored in the server, execute a second session for calculating a specific keep alive value corresponding to a period in which an IP address mapped by the NAT expires, by:
• controlling the communication unit to transmit a first time value to the server in the second session;
• identifying whether a response is received from the server after a time corresponding to the first time value is elapsed;
• when the response is received, increasing the first time value by a unit time and iteratively retransmitting the increased first time value to the server;
• when the response is not received, setting a time value which is the unit time subtracted from the corresponding first time value as a specific keep alive value of the first session;
• and
• finishing the second session, and
• wherein the controller is configured to transmit a connection IP address, connection environment information, device information for calculating the specific keep alive value, and the calculated specific keep alive value to the server,
• wherein the specific keep alive value corresponds to a maximum value of a time during which the IP address is maintained without being changed.