Open System Services System Calls Reference Manual (G06.25+, H06.03+)

System Functions (s and S) setsockopt(2)
SO_REUSEPORT
Specifies whether the rules used in validating ports supplied by a
bind( ) function call should allow reuse of local ports. The
default value used for the option when the socket is created is 0
(zero), which indicates that ports should not be reused.
This option is valid only for UDP ports.
This option takes an int value. Specifying a nonzero value per-
mits ports to be reused.
SO_SNDBUF Sets the send buffer size in bytes. The default value used for the
option when the socket is created is 8K bytes.
This option is valid only for AF_INET or AF_INET6 sockets.
If this option is specified for sockets of other types, the function
call fails and sets errno to [ENOPROTOOPT].
option_value takes an int value. Specifying a 0 (zero) value, a
negative value, or a value greater than 262144 causes the func-
tion call to fail with errno set to [EINVAL].
The IPPROTO_TCP (TCP protocol-level) options are:
TCP_MAXRXMT
Sets the maximum retransmission timeout value in multiples of
500 milliseconds.
option_value takes an int value. Valid values are in the range 1
through 60. The value specified for this option should be greater
than or equal to the value used for the TCP_MINRXMT option.
TCP_MINRXMT
Sets the minimum retransmission timeout value in multiples of
500 milliseconds.
option_value takes an int value. Valid values are in the range 1
through 2400. The value specified for this option should be less
than or equal to the value used for the TCP_MAXRXMT
option.
TCP_NODELAY
Specifies whether data packets are buffered before transmission.
option_value takes an int value. A nonzero value indicates that
data packets should not be buffered. A 0 (zero) value indicates
that buffering should occur.
TCP_RXMTCNT
Sets the maximum retransmission count.
option_value takes an int value. Valid values are in the range 1
through 12. When the value specified for this option is multi-
plied by the value used for the TCP_MAXRMT option and the
result is less than the value used for TCP_TOTRXMTVAL, the
TCP connection will be dropped before the
TCP_TOTRXMTVAL value is reached.
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