SCTP Programmer's Guide

If SCTP does not call the bind() API before calling connect() , the application picks

a transient port and chooses an address set that is equivalent to binding with

INADDR_ANY and IN6ADDR_ANY for IPv4 and IPv6 sockets, respectively. One of these

addresses serves as the primary address for the association. When an application calls

bind() with the INADDR_ANY or the IN6ADDR_ANY_INIT wildcard address, the

multihoming feature is enabled in SCTP.

The close() Socket API

Applications use close() to gracefully close down an association.

Following is the syntax for the close() socket API:

int close(int sd);

where:

Represents the socket descriptor of the association to be closed.

After an application calls close() on a socket descriptor, no further socket operations

succeed on that descriptor.

The shutdown() Socket API

Applications use the shutdown() socket API to disable send or receive operations at

an endpoint. The effect of the shutdown() call is different in SCTP and TCP. In TCP,

a connection is in half-closed state even after an application calls shutdown(). In the

half-close state, an application at the sending endpoint continues to send data even if

an application at the receiving endpoint has stopped receiving data. In SCTP,

shutdown() completely disables applications at both the endpoints from sending or

receiving data.

NOTE: Applications can use the SCTP streams feature to achieve the half closed state

in SCTP.

Following is the syntax for the shutdown() socket call:

int shutdown(int sd, int how);

Specifies the socket descriptor of the association that needs to be closed.

how

Specifies the type of shutdown. The values are as follows:

SHUT_RD

Disables further receive operations

SHUT_WR

Disables further send operations and initiates the SCTP shutdown

sequence

SHUT_RDWR

Disables further send and receive operations, and initiates the

SCTP shutdown sequence

In SCTP, SHUT_WR initiates an immediate and full protocol shutdown. In TCP, SHUT_WR

causes TCP to enter a half-closed state. The SHUT_RD value behaves in the same way

for SCTP and TCP. SCTP_WR closes the SCTP association while leaving the socket

46 SCTP Socket APIs