| Value | Meaning |
|---|---|
| None | |
| TCP_NODELAY | 1: Don't delay send to coalesce packets |
| TCP_MAXSEG | 2: Set maximum segment size |
| TCP_CORK | 3: Control sending of partial frames |
| TCP_KEEPIDLE | 4: Start keeplives after this period |
| TCP_KEEPINTVL | 5: Interval between keepalives |
| TCP_KEEPCNT | 6: Number of keepalives before death |
| TCP_SYNCNT | 7: Number of SYN retransmits |
| TCP_LINGER2 | 8: Life time of orphaned FIN-WAIT-2 state |
| TCP_DEFER_ACCEPT | 9: Wake up listener only when data arrive |
| TCP_WINDOW_CLAMP | 10: Bound advertised window |
| TCP_INFO | 11: Information about this connection. |
| TCP_QUICKACK | 12: Bock/reenable quick ACKs. |
| TCP_CONGESTION | 13: Congestion control algorithm. |
| TCP_MD5SIG | 14: TCP MD5 Signature (RFC2385) |
TCP option codes supported by getsockopt()/setsockopt() (from <inet/netinet.h>).