sendto

#include <rtl.h>

int sendto (
    int sock,          /* Socket descriptor */
    const char *buf,   /* Pointer to a buffer with data */
    int len,           /* Length of data in bytes */
    int flags,         /* Message flags */
    SOCKADDR *to,      /* Pointer to destination address */
    int tolen);        /* Length of the address structure */

The sendto function is used to send data on a SOCK_DGRAM socket type.

The argument sock specifies a socket descriptor returned from a previous call to socket.

The argument buf is a pointer to the application data buffer containing data to transmit. The buffer data length is not limited in size. If the data length is too large for one packet, the send function will fragment the data and send it in several successive data packets:

• In blocking mode, which is enabled if the system detects RTX environment, this function returns after the data has been successfully transmitted.
• In non blocking mode, the function returns immediately without blocking the system. Return value represents the numbytes sent, which can be less than len, if the data can not be transmitted in one packet.

The argument len specifies the length of data in bytes.

The argument flags specifies the message flags:

The argument to is a pointer to the SOCKADDR structure that contains the end point node IP address and port number.

The argument tolen specifies the length of SOCKADDR structure.

The sendto function is in the RL-TCPnet library. The prototype is defined in rtl.h.

note

• You must call the socket function before any other function calls to the BSD socket.
• If a negative number is returned, it represents an error code.

The send function returns the result code:

• numbytes
  The total number of bytes successfully sent (a positive number).
• SCK_EINVALID
  The socket identified with sock is invalid, or in invalid state.
• SCK_EINVALIDPARA
  The function parameters are invalid or not supported.
• SCK_EWOULDBLOCK
  The function would block, and the socket is set to non blocking mode.
• SCK_ECLOSED
  Remote end point has closed the connection.
• SCK_ERROR
  The function failed due to error in underlying native TCP/UDP socket.
• SCK_ELOCKED
  The socket is locked by another task in RTX environment.

ioctlsocket, recv, recvfrom, send

#include <rtl.h>

__task void client (void) {
  /* LED Control client task. */
  SOCKADDR_IN to;
  int sock, res;
  char dbuf[4];
  U8 p2val,lshf;

  while (1) {
    sock = socket (AF_INET, SOCK_DGRAM, 0);

    to.sin_port      = htons(1001);
    to.sin_family    = PF_INET;
    to.sin_addr.s_b1 = 192;
    to.sin_addr.s_b2 = 168;
    to.sin_addr.s_b3 = 0;
    to.sin_addr.s_b4 = 100;

    lshf  = 1;
    p2val = 0x01;
    while (1) {
      /* Shift the LEDs */
      LED_out (p2val);
      p2val = lshf ? (p2val << 1) : (p2val >> 1);
      if (p2val == 0x80) lshf = 0;
      if (p2val == 0x01) lshf = 1;

      /* Send the data to LED Server. */
      dbuf[0] = BLINKLED;
      dbuf[1] = p2val;
      res = sendto (sock, (char *)&dbuf, 2, 0, (SOCKADDR *)&to, sizeof (to));
      if (res < 0) {
        break;
      }
      os_dly_wait (50);
    }
    closesocket (sock);
  }
}