Sends the data to a specific destination.
- Parameters
-
| s | Descriptor, identifying a socket. |
| buf | Buffer containing the data to be transmitted. |
| len | Length of the data in buf. |
| flags | Optional flag specifying the way, in which the call is made. It can be constructed by using the bitwise OR operator with any of the values defined by the fnet_msg_flags_t. |
| to | Pointer to the address of the target socket. |
| tolen | Size of the address in to. |
- Returns
- This function returns:
- The total number of bytes sent, if no error occurs. It can be lesser than the number indicated by
len.
- FNET_ERR if an error occurs.
The specific error code can be retrieved using the fnet_error_get().
- See also
- fnet_socket_connect(), fnet_socket_send()
For nonb-locking stream-oriented sockets (SOCK_STREAM), the number of actually sent bytes can be between 1 and the requested length, depending on buffer availability on both client and server machines.
For message-oriented sockets (SOCK_DGRAM), care must be taken not not exceed the maximum datagram size, which can be obtained by using the fnet_socket_getopt() to retrieve the value of the socket option SO_SNDBUF. If the data is too long to pass atomically through the underlying datagram protocol, the error FNET_ERR_MSGSIZE is returned and no data is transmitted.
Calling fnet_socket_sendto() with a zero len parameter is permissible. In such cases, the fnet_socket_sendto() will return zero as a valid value, and for message-oriented sockets (SOCK_DGRAM), a zero-length transport datagram is sent.
The fnet_socket_sendto() function is normally used on a connectionless socket (SOCK_DGRAM) to send a datagram to a specific peer socket identified by the to parameter. Even if the connectionless socket has been previously connected to a specific address, the to parameter overrides the destination address for that particular datagram only.
On a connection-oriented socket (SOCK_STREAM), the to and tolen parameters are ignored, making the fnet_socket_sendto() equivalent to fnet_socket_send().
The flags parameter can be used to influence the behavior of the function invocation beyond the options specified for the associated socket.
