I've always assumed that Nagle's algorithm affected the socket in both directions, and that setting TCP_NODELAY somehow informed the remote end also to switch off Nagle.
Is that right, or does setting TCP_NODELAY only affect the behaviour of the end that calls it?
TCP_NODELAY affect sending TCP segments only on the host that sets this option on its socket. That is, the peer's sending algorithm is not affected.
来源：https://stackoverflow.com/questions/8226512/does-setting-tcp-nodelay-affect-the-behaviour-of-both-ends-of-the-socket