---
name: "sctp_connectx"
section: "3"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["linux", "freebsd"]
url: "https://new.carta.tech/sctp_connectx"
---

# sctp\_connectx(3)

connect an SCTP socket with multiple destination addresses

## NAME

**sctp\_connectx** – connect an SCTP socket with multiple destination addresses

## LIBRARY

Standard C Library (libc, -lc)

## SYNOPSIS

**#include \<sys/types.h\>**

**#include \<sys/socket.h\>**

**#include \<netinet/sctp.h\>**

*int*\

**sctp\_connectx**(*int sd*, *struct sockaddr \*addrs*, *int addrcnt*, *sctp\_assoc\_t \*id*);

## DESCRIPTION

The **sctp\_connectx**() call attempts to initiate an association to a peer SCTP endpoint. The call operates similarly to **connect**() but it also provides the ability to specify multiple destination addresses for the peer. This allows a fault tolerant method of initiating an association. When one of the peers addresses is unreachable, the subsequent listed addresses will also be used to set up the association with the peer.

The user also needs to consider that any address listed in an **sctp\_connectx**() call is also considered "confirmed". A confirmed address is one in which the SCTP transport will trust is a part of the association and it will not send a confirmation heartbeat to it with a random nonce.

If the peer SCTP stack does not list one or more of the provided addresses in its response message then the extra addresses sent in the **sctp\_connectx**() call will be silently discarded from the association. On successful completion the provided *id* will be filled in with the association identification of the newly forming association.

## RETURN VALUES

The call returns 0 on success and -1 upon failure.

## ERRORS

The **sctp\_connectx**() function can return the following errors:

- \[EINVAL\]

  An address listed has an invalid family or no addresses were provided.

- \[E2BIG\]

  The size of the address list exceeds the amount of data provided.

- \[EBADF\]

  The argument *s* is not a valid descriptor.

- \[ENOTSOCK\]

  The argument *s* is not a socket.

## SEE ALSO

[connect(2)](/connect/2.md), [sctp(4)](/sctp/4.md) R. Stewart, M. Tuexen, K. Poon, P. Lei, and V. Yasevich, *Sockets API Extensions for the Stream Control Transmission Protocol (SCTP)*, RFC 6458, December 2011.

## STANDARDS

The **sctp\_connectx**() function conforms to RFC 6458.