What are tcp data streams and message segments?

Source port and destination port: Each occupies 2 bytes. The 16-bit port number plus the 32-bit IP address together form an address equivalent to the transport layer service access point, that is, " "Socket";

These ports can be used to multiplex several high-level protocols downward;

The sequence number field and the confirmation sequence number field:

Serial number: 4 characters Section is the sequence number of the first byte of the data item group sent in this message segment. In the data stream transmitted by TCP, each byte has a sequence number. For example, if the sequence number of a message segment is 300, and the initial data supply is 100 bytes, the sequence number of the next message segment is 400;

Confirmation sequence number: occupies 4 bytes, which is expected to be received by the other party The sequence number of the first byte of the data sent next time is the sequence number in the header of the next message segment expected to be received;

Because the sequence number field is 32 bits long, it can be used for 4GB The data is numbered to ensure that when the serial number is reused, the data with the old serial number has already disappeared in the network;