@CHIP-RTOS C Library - TCP/IP API

recvfrom_bsd

Receive a UDP datagram.

int far recvfrom_bsd ( int sd,
                   char far * bufptr,
                   int buflen,
                   int flags,
                   struct sockaddr far * fromPtr,
                   int far * fromLengthPtr,
                   unsigned long timeout ) ;

Parameters

sd

Socket descriptor

bufptr

Output Parameter:   Received data will be put here.

buflen

Maximum bytes to write to the buffer at bufptr .

flags

Control flags:   Either MSG_BLOCKING or MSG_DONTWAIT.

fromPtr

Output Parameter:   Pointer to a sockaddr_in (IPv4) or sockaddr_in6 (IPv6) data structure, which will be set to indicate from where the received data originated.   This pointer can be set to NULL if this information is not desired.

fromLengthPtr

Input/Output Parameter:   The integer referenced by this pointer must be set prior to calling to the length of the object at fromPtr .   If fromPtr is NULL, then this parameter is not required and can be set to NULL.   On return the length of object written o fromPtr will be reported here.

timeout

Maximum wait time in milliseconds.   Set to zero to wait forever.

Return Value

> 0: Number of data bytes placed at bufptr .
-1:   Failure, error code is available using get_socketerror().

Comments

This API applies to UDP sockets.

If the waiting datagram at the internal socket receive queue has a size larger than the specified bufLen , the return value will be -1 and error code 240 ("Message too long") will be reported by the get_socketerror() in this case.   The receive buffer contains the truncated datagram.

This function's prototype takes a pointer to the generic type sockaddr for its fromPtr parameter,for compatibility between IPv4 and IPv6 protocols.   The pointer to the sockaddr_in (IPv4) or sockaddr_in6 (IPv6) data structure which is actually used should be cast to a sockaddr type pointer to avoid compiler warnings, "Suspicious pointer conversion".

If the compilation switch

     #define BSD44_SOCKET_API_STYLE

is set as a global define in the user application prior to including the Beck C-library header files, the recvfrom() call can be used in BSD 4.4 compatible style with the parameters specified above.   Using this switch the CLIB TCPIP_Socket.H redefines recvfrom() to recvfrom_bsd() .

See Also

sendto_bsd        recv_bsd        opensocket
Set_Blocking_Mode        select        select_ms
recvfrom        get_socketerror        

RTOS API

On the first call, this library function invokes a software interrupt which modifies the code at the calling site inside your application program.   A direct FAR JMP into the @CHIP-RTOS-x86 implementation for this function is installed so that on return and on any subsequent calls to this API this dynamic link reaches the function's implementation directly.

Supported since or modified in @CHIP-RTOS version

SC12	SC13	SC11	SC1x3	SC2x
n/a	n/a	n/a	V1.36	V1.36

Supported by @CHIP-RTOS C Library since version

CLIB
V2.20