TH_FIN = 0x01
TH_SYN = 0x02
TH_RST = 0x04
TH_PUSH = 0x08
TH_ACK = 0x10
TH_URG = 0x20
TCPOPT_EOL = 0
TCPOPT_NOP = 1
TCPOPT_MAXSEG = 2
TCP_MSS = 512
TCP_MAXWIN = 65535
TCP_NODELAY = 0x01
TCP_MAXSEG = 0x02
