6.2.3.8 send

The send function is used by the application to send data to a remote host. The send function can be used to send either UDP or TCP data depending on the type of socket.

For a TCP socket a connection must be established first.
For a UDP socket, the recommended way is to use sendto API, where the destination address is defined. However, it is possible to use send API instead of sendto API. For this, at least one successful call must be made to sendto API prior to the consecutive calls of send function. This ensures that the destination address is saved in the ATWINC15x0 firmware.

The send function generates a SOCKET_MSG_SEND event callback after the data is transmitted to the remote host. For TCP sockets, this event guarantees that the data is delivered to the remote host TCP/IP stack (the remote application must use the recv function to read the data). For UDP sockets, it means that the data is transmitted, but there is no guarantee that the data is delivered to the remote host as per UDP protocol. The application is responsible to guarantee data delivery in the UDP sockets case.

The SOCKET_MSG_SEND event callback returns the size of the data transmitted of the transmission in the success case and zero or negative value in case of an error. The maximum size of data buffer that can be transmitted using the socket APIs is 1400 bytes.