send(), sendto() - send a message from a socket
#include <sys/types.h>
#include <sys/socket.h>
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, int tolen)
The send(2) and sendto(2) functions are used to transmit a message to another socket. The send(2) functionmay be used only when the socket is in a connected state, while sendto(2) may be used at any time.
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.
No indication of failure to deliver is implicit in a send(2). Locally detected errors are indicated by a return value of -1.
If no messages space is available at the socket to hold the message to be transmitted, then send(2) normally blocks, unless the socket has been placed in non-blocking I/O mode. 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:
| MSG_OOB | process out-of-band data |
| MSG_DONTROUTE | bypass routing, use direct interface |
The flag MSG_OOB is used to send 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 is usually used only by diagnostic or routing programs.
The call returns the number of characters sent, or -1 if an error occurred.
The send(2) and sendto(2) calls fail if:
fcntl(2)
recv(2)
select(2)
getsockopt(2)
socket(2)
write(2)