tfZeroCopySendTo

Table of Contents >> Programmer's Reference

#include <trsocket.h>

int tfZeroCopySendTo	(
	int socketDescriptor,
	ttUserMessage bufferHandle,
	int bufferLength,
	int flags,
	const struct sockaddr TM_FAR * toAddressPtr,
	int toAddressLength
	);

Function Description

This function is used to send a zero copy message. It operates identically to sendto() with the exception that it takes a zero copy buffer handle as a parameter.

Note:

Once tfZeroCopySendTo() is called, the caller does NOT own the buffer and it is freed by the TCP/IP stack, except when if fails with a TM_EWOULDBLOCK error code, in which case the user can either try and send the buffer at a later time, or free the zero copy buffer using tfFreeZeroCopyBuffer().

Parameters

• socketDescriptor

  The socket descriptor to send data to.

• bufferHandle

  The zero copy buffer that contains the message.

• bufferLength

  The length of the message to send.

• flags

  See below for possible flags parameters that can be OR'ed together.

• toAddressPtr

  The address to send the packet to.

• toAddressLength

  The length of the destination address.

Flags

Value	Meaning
MSG_DONTWAIT	Don't wait for data, but rather return immediately.
MSG_DONTROUTE	The SO_DONTROUTE optoin is turned on for the duration of this operation. Only diagnostic or routing progrms use it.
MSG_SCATTERED	Set this flag when sending a scattered zero copy recv buffer received with tfZeroCopyRecvFrom(). Note that to send a user scattered buffer (not obtained via a call to tfZeroCopyRecvFrom()) then tfSocketScatteredSendTo() can be used.

Returns

• >= 0

  The number of bytes sent.

• TM_SOCKET_ERROR

  Failure.

Note:

TM_SOCKET_ERROR means that this socket call has failed and the errorCode has been set on the socket itself. To retrieve the socket error the user must call tfGetSocketError(socketDescriptor).

Possible socket errors

• TM_EBADF

  The socket descriptor is invalid.

• TM_EHOSTUNREACH

  No route to destination.

• TM_ECONNREFUSED

  The socket received an ICMP destination unreachable message from the remote host. This typically means that the receiver is not listening on the remote port.

• TM_EMSGSIZE

  The socket requires that the message be sent atomically and the message was too long.

• TM_EPROTOTYPE

  The TCP protocol requires usage of tfZeroCopySend() not tfZeroCopySendTo().

• TM_EWOULDBLOCK

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

• TM_EFAULT

  'bufferHandle' does not correspond to a zero copy buffer.

• TM_EINVAL

  One of the following:

• bufferLength is less than or equal to 0.
• flags is something besides what is listed above.
• toAddressPtr is null.
• toAddressLength does not equal sizeof(struct sockaddr_in).

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