TCP header field definitions
Short descriptions of each of the Transmission Control Protocol (TCP) fields follow.
|Source Port||Identifies the port number of a source application program.|
|Destination Port||Identifies the port number of a destination application program.|
|Sequence Number||Specifies the sequence number of the first byte of data in this segment.|
|Acknowledgment Number||Identifies the position of the highest byte received.|
|Data Offset||Specifies the offset of data portion of the segment.|
|Reserved||Reserved for future use.|
|Code|| Control bits to identify the purpose of the segment:
|Window||Specifies the amount of data the destination is willing to accept.|
|Checksum||Verifies the integrity of the segment header and data.|
|Urgent Pointer||Indicates data that is to be delivered as quickly as possible. This pointer specifies the position where urgent data ends.|
The applications programming interface to TCP consists of a set of library subroutines provided by the sockets interface.