TCP Options
You can use the options in this section with a protocol level of INET_TCP. These TCP options are not association-related. They may be negotiated in all endpoint states except T_UNBND and T_UNINIT. They are read-only in state T_UNBND.
#define TCP_NODELAY 0x01 /* set TCP delay mode */
#define TCP_MAXSEG 0x02 /* read max segment size */
#define TCP__NOTIFY_THRESHOLD 0x10 /* reserved */
#define TCP_ABORT_THRESHOLD 0x11 /* reserved */
#define TCP__CONN_NOTIFY_THRESHOLD 0x12 /* reserved */
#define TCP_CONN_ABORT_THRESHOLD 0x13 /* reserved */
#define TCP_OOBINLINE 0x14 /* reserved */
#define TCP_URGENT_PTR_TYPE 0x15 /* reserved */
#define TCP_KEEPALIVE OPT_KEEPALIVE/* activate keep-alive timer */
};
Option descriptions
TCP_NODELAY
- Set the TCP delay mode. By default, when TCP has a full segment's worth of data, it sends the segment immediately; but if it receives less than a segment's worth of data and has not yet received acknowledgment for the last packet sent, it saves the data until it either receives a full segment's worth, it receives acknowledgment for the last packet, or until a timeout period has expired. (In this context, a full segment is the maximum-sized unit of data that can be sent by TCP at one time and a packet is data that is transmitted as a single unit. ) Specify
T_YES for this option to cause all data to be sent immediately. Specify T_NO to return TCP to the default delay mode. A request to set this option to no delay is an absolute requirement.
TCP_MAXSEG
- Read the maximum TCP segment size. The maximum segment size is returned as an unsigned long specifying the number of octets. This option is read-only.
TCP_NOTIFY_THRESHOLD
- Reserved.
TCP_ABORT_THRESHOLD
- Reserved.
TCP_CONN_NOTIFY_THRESHOLD
- Reserved.
TCP_CONN_ABORT_THRESHOLD
- Reserved.
TCP_OOBINLINE
- Reserved.
TCP_URGENT_PTR_TYPE
- Reserved.
TCP_KEEPALIVE
- Activate the keep-alive timer. If this option is set on, TCP monitors idle connections and sends a keep-alive packet to check a connection after a preset time has expired. You use a
t_kpalive structure, described later in this section, to specify the value of this option. The default state for the keep-alive timer is off. A request to activate or deactivate the keep-alive timer is an absolute requirement.
The TCP_KEEPALIVE option uses a t_kpalive structure, defined as follows:
struct t_kpalive {
long kp_onoff; /* option on/off */
long kp_timeout; /* timeout in minutes */
};
Field Description
kp_onoff
- Activate or deactivate the keep-alive timer. Set this field to
T_YES to activate the timer or to T_NO to deactivate it. A request to activate or deactivate the timer is an absolute requirement. The default value of this field is T_NO. The Open Transport TCP implementation does not support the value T_YES|T_GARBAGE for this field.
kp_timeout
- Set the requested timeout value, in minutes. Specify a value of
T_UNSPEC to use the default value. You may specify any positive value for this field of 120 minutes or greater. The timeout value is not an absolute requirement; if you specify a value less than 120 minutes, TCP will renegotiate a timeout of 120 minutes.
