SEND

NAME

SYNOPSIS

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

int sendto(int s, const void *msg, int len, unsigned int flags, const struct sockaddr *to, int tolen);
int sendto_secure(int s, const void *msg, int len, unsigned int flags, const struct sockaddr *to, int tolen, security_id_t dso_sid, security_id_t msg_sid);

int sendmsg(int s, const struct msghdr *msg, unsigned int flags);
int sendmsg_secure(int s, const struct msghdr *msg, unsigned int flags, security_id_t dso_sid, security_id_t msg_sid);  

DESCRIPTION

The address of the target is given by to with tolen specifying its size. The length of the message is given by len. If the message is too long to pass atomically through the underlying protocol, the error EMSGSIZE is returned, and the message is not transmitted.

If the socket is of type SOCK_DGRAM, then sendto_secure and sendmsg_secure calls may be used to specify the desired SID of the destination socket using the dso_sid parameter and/or the SID of the message using the msg_sid parameter. By default, messages are labeled with the SID of the sending socket.

No indication of failure to deliver is implicit in a send. Locally detected errors are indicated by a return value of -1.

When the message does not fit into the send buffer of the socket, send normally blocks, unless the socket has been placed in non-blocking I/O mode. In non-blocking mode it would return EAGAIN in this case. The select(2) call may be used to determine when it is possible to send more data.

The flags parameter may include one or more of the following:

#define MSG_OOB           0x1     /* process out-of-band data */
#define MSG_DONTROUTE     0x4     /* bypass routing, use direct interface */
#define MSG_DONTWAIT      0x40    /* don't block */ 
#define MSG_NOSIGNAL      0x2000  /* don't raise SIGPIPE */ 

MSG_OOB

Sends out-of-band data on sockets that support this notion (e.g. SOCK_STREAM); the underlying protocol must also support out-of-band data.

MSG_DONTROUTE

Bypasses the usual routing table lookup and sends the packet directly to the interface described by the destination address. This is usually used only by diagnostic or routing programs.

MSG_DONTWAIT

Enables non-blocking operation; if the operation would block, EAGAIN is returned.

MSG_NOSIGNAL

Requests not to send SIGPIPE on errors on stream oriented sockets when the other end breaks the connection. The EPIPE error is still returned.

See recv(2) for a description of the msghdr structure. You may send control information using the msg_control and msg_controllen members. The maximum control buffer length the kernel can process is limited by the net.core.optmem_max sysctl; see socket(4).  

RETURN VALUES

ERRORS

EBADF

An invalid descriptor was specified.

ENOTSOCK

The argument s is not a socket.

EFAULT

An invalid user space address was specified for a parameter.

EMSGSIZE

The socket requires that message be sent atomically, and the size of the message to be sent made this impossible.

EAGAIN

The socket is marked non-blocking and the requested operation would block.

ENOBUFS

The system was unable to allocate an internal memory block. The operation may succeed when buffers become available.

EINTR

A signal occurred.

ENOMEM

No memory available.

EINVAL

Invalid argument passed.

EPIPE

The local end has been shut down on a connection oriented socket. In this case the process will also receive a SIGPIPE unless MSG_NOSIGNAL is set.

CONFORMING TO

SEE ALSO

Index

NAME

SYNOPSIS

DESCRIPTION

RETURN VALUES

ERRORS

CONFORMING TO

SEE ALSO