send.2 (2010 09)

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send(2) send(2)

NAME

send(), sendmsg(), sendto() - send a message from a socket

SYNOPSIS

#include <sys/socket.h>

int send(int s, const void *msg, int len, int flags);

int sendto(

int s,

const void *msg,

int len,

int flags,

const void *to,

int tolen

);

int sendmsg(int s, const struct msghdr msg[], int flags);

UNIX 03 Only (X/Open Sockets)

ssize_t send(int s, const void *msg, size_t len, int flags);

ssize_t sendto(

int s,

const void *msg,

size_t len,

int flags,

const struct sockaddr *to,

socklen_t tolen

);

ssize_t sendmsg(int s, const struct msghdr *msg, int flags);

Obsolescent UNIX 95 Only (X/Open Sockets)

ssize_t sendto(

int s,

const void *msg,

size_t len,

int flags,

const struct sockaddr *to,

size_t tolen

);

DESCRIPTION

The send(), sendmsg(), and sendto() system calls transmit a message to another socket. send()

can be used only when the socket is in a connected state, whereas sendmsg() and sendto() can be

used at any time. sendmsg() allows the send data to be gathered from several buffers speciﬁed in the

msghdr structure.

s is a socket descriptor that speciﬁes the socket on which the message will be sent.

msg points to the buffer containing the message.

If the socket uses connection-based communications, such as a SOCK_STREAM socket, these calls can

only be used after the connection has been established (see connect (2)). In this case, any destination

speciﬁed by to is ignored. For connectionless sockets, such as SOCK_DGRAM,

sendto() must be used

unless the destination address has already been speciﬁed by connect(). If the destination address has

been speciﬁed and sendto() is used, an error results if any address is speciﬁed by to.

The address of the target socket is contained in a socket address structure pointed to by to, with tolen

specifying the size of the structure.

If a

sendto() is attempted on a SOCK_DGRAM socket before any local address has been bound to it,

the system automatically selects a local address to be used for the message. In this case, there is no

guarantee that the same local address will be used for successive sendto() requests on the same socket.

The length of the message is given by len in bytes. The length of data actually sent is returned. If the

message is too long to pass atomically through the underlying protocol, the message is not transmitted,

HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1

Summary of content (6 pages)

PAGE 1
send(2) send(2) NAME send(), sendmsg(), sendto() - send a message from a socket SYNOPSIS #include
PAGE 2
send(2) send(2) −1 is returned, and errno is set to [EMSGSIZE]. For SOCK_DGRAM sockets, this size is fixed by the implementation (see the DEPENDENCIES section). Otherwise there is no size limit. When send() or sendto() returns a positive value, it only indicates this number of bytes have been sent to the local transport provider. It does not mean this number of bytes have been delivered to the peer socket application. A SOCK_DGRAM socket does not guarantee end-to-end delivery.
PAGE 3
send(2) send(2) • If there is enough space available in the system to buffer all of the data, send() completes successfully, having written out all of the data, and returns the number of bytes written. • If there is not enough space in the buffer to write out the entire request, send() completes successfully, having written as much data as possible, and returns the number of bytes it was able to write.
PAGE 4
send(2) send(2) socklen_t struct int void socklen_t int msg_namelen; iovec *msg_iov; msg_iovlen; *msg_control; msg_controllen; msg_flags; /* /* /* /* /* /* size of address */ scatter array for data */ # of elements in msg_iov */ ancillary data, see below */ ancillary data buffer len */ flags on received message */ /* /* /* /* /* /* /* optional address */ size of address */ scatter array for data */ # of elements in msg_iov */ ancillary data, see below */ ancillary data buffer len */ flags on received
PAGE 5
send(2) send(2) [EACCES] Process doing a send() of a broadcast packet does not have broadcast capability enabled for the socket. Use setsockopt() to enable broadcast capability. [EAFNOSUPPORT] The specified address is not a valid address for the address family of this socket. [EAGAIN] Nonblocking I/O is enabled using the O_NONBLOCK flag with fcntl(), and the requested operation would block, or the socket has an error that was set asynchronously.
PAGE 6
send(2) send(2) its peer. [ENOTSOCK] s is a valid file descriptor, but it is not a socket. [EOPNOTSUPP] The MSG_OOB flag was specified; it is not supported for AF_UNIX or AF_VME_LINK sockets. [EPIPE] and SIGPIPE signal An attempt was made to send on a socket that was connected, but the connection has been shut down either by the remote peer or by this side of the connection.