sendto

sendto transmits a message on a non-connected non-TCP socket.

Syntax

int sendto(
    SOCKET s,
    const char *buf,
    int len,
    int flags,
    const struct sockaddr *to,
    int tolen
);

Parameters

s

Socket descriptor for a connected socket.

buf

A pointer to a character buffer that holds the data to send.

len

An integer containing the size, in bytes, of the character buffer buf.

flags

A set of flags arguments that is logical OR of one or more of the following.

Flag	Description
MSG_DONTROUTE	Send without using routing tables (not currently supported).
MSG_OOB	Process urgent data, SOCK_STREAM only.

to

Pointer to the sockaddr structure of the target host.

tolen

Size of the sockaddr structure associated with to.

Return Value

The number of bytes sent if the function succeeds, SOCKET_ERROR if the function fails

Use WSAGetLastError to retrieve a specific error code.

Remarks

The send and sendto functions are used to transmit a message to another socket. The send function can only be used when the socket is in a connected state. The sendto function includes the additional parameters to, which specifies a target address and tolen, which specifies the address size.

At present, sendto only works with an unconnected socket and requires the address pointer to be non-NULL and address length to be >= of sizeof(struct sockaddr_in) or >= sizeof(struct sockaddr_in6).

You must set Scope ID when sending data to a link-local IPv6 address. Otherwise, sendto will fail.

If the message is too long to pass through the underlying protocol and the protocol does not support fragmentation, SOCKET_ERROR is returned and WSAEMSGSIZE is the last error set.