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5.2.2 UDP

The UDP is a Connection-less protocol. It communicates without “connection SOCKET.”

The TCP protocol guarantees reliable data communication, but the UDP protocol uses

datagram communication which has no guarantees of data communication. Because the

UDP does not use “connection SOCKET,” it can communicate with many other devices

with the known host IP address and port number. This is a great advantage;

communication with many others by using just one SOCKET, but also it has many

problems such as loss of transmitted data, unwanted data received from others, etc. To

avoid these problems and guarantee reliability, the host retransmits damaged data or

ignores the unwanted data which is received from others. The UDP protocol supports

unicast, broadcast, and multicast communication. It follows the below communication

flow.

Figure 12 UDP Operation Flow

5.2.2.1

Unicast and Broadcast

The unicast is one method of UDP communication. It transmits data to one destination

at one time. On the other hand, the broadcast communication transmits data to all

receivable destinations by using ‘broadcast IP address (255.255.255.255)’. For example,

suppose that the user transmits data to destination A, B, and C. The unicast

communication transmits each destination A, B, and C at each time. At this time, the

ARPTO can also occur when the user gets the destination hardware address of

destinations A, B and C. User cannot transmit data to destinations which have ARPTO.

The broadcast communication can simultaneously transmit data to destination A, B and

C at one time by using “255.255.255.255” or “local address | (~subnet address)” IP

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