Structure of TCP/UDP header
puchi-engineerStructure of the TCP header
To understand TCP communication, it is necessary to understand what is contained in the TCP header. TCP establishes a connection prior to communication, and performs acknowledgment and flow control, so the TCP header structure is much more complicated than the UDP packet structure. A typical TCP header size is 20 bytes large.
| field | explanation |
| Source port number (16 bits) | A number that identifies the sending application. Unlike UDP, TCP cannot have a source port number of 0. Available from 1 to 65535. |
| Destination port number (16 bits) | A number that identifies the destination application. Available from 1 to 65535. *0 is reserved |
| Sequence number (32 bits) | Number for ordering data to be sent. Increment the sequence number by 1 for each byte of data sent. 2 If it exceeds 32 , repeat the same number again. |
| Acknowledgment number (32 bits) | A field that indicates how much of the received data has been received by byte position. Returns the sequence number + 1 of the received data position. The ACK number field is valid only when the ACK flag is ON. |
| Header length (4 bits) | A fie |