TCP, itself, will send a RST.
This is explained in RFC 793, Transmission Control Protocol:
If the connection does not exist (CLOSED) then a reset is sent in response to any incoming segment except another reset. In particular, SYNs addressed to a non-existent connection are rejected by this means.
If the incoming segment has an ACK field, the reset takes its sequence number from the ACK field of the segment, otherwise the reset has sequence number zero and the ACK field is set to the sum of the sequence number and segment length of the incoming segment. The connection remains in the CLOSED state.
By the way, TCP does not know anything about clients or servers. TCP creates connections between peers. The client/server concept is for applications, which are off-topic here.
