Which of the TCP flags represents data in the packet?

The PSH (Push) flag in the TCP header instructs the receiving host to push the data to the receiving application immediately without waiting for the buffer to fill. This is used to ensure that data is not delayed, thus improving the efficiency of communication where real-time data processing is required. It effectively tells the system that the data in the packet should be considered urgent.References:

Douglas E. Comer, "Internetworking with TCP/IP Vol.1: Principles, Protocols, and Architecture".