Chapter 36. Controlling MagicQ using UDP/IP

Enable ChamSys Remote Ethernet Protocol in the View Settings view of the Setup Window.

ChamSys Remote Ethernet Protocol is an open protocol – i.e. you do not need permission to use it for your own purposes. It is a UDP/IP based protocol using port 6553 in broadcast mode.

The port number can be changed in setup, View Settings, Network, Playback Sync Port.

The structure of the UDP/IP packets are a ChamSys CREP header followed by the remote commands:

long32 chamsys;
word16 version;
byte seq_fwd;
byte seq_bkwd;
word16 length;
byte data;

where long32 is 4 bytes, word16 is 2 bytes and byte is 1 byte.

ChamSys is 4 characters C R E P. Note that on MagicQ this is stored as little-endian, so that on the network it will appear as P E R C.

The version is initially 0 and allows for future expansion of the protocol.

The fwd sequence number is an incrementing sequence number. It enables the receiving end to determine if packets are missed. In addition the receiving end should sends back the last sequence number it received in the backward sequence number.

Length is the length of the data field. It does not include the length of the ChamSys header.

From v1.6.6.0 support is added for ChamSys Remote Ethernet Protocol Messages without the ChamSys CREP header - this allows easier integration with external systems but reduces the amount of checking of messages performed. In Setup, View Settings, Network, set Ethernet remote protocol to "ChamSys Rem (rx no header)", "ChamSys Rem (tx no header), or "ChamSys Rem (tx + rx no header)".

Commands are transmitted from the network port using the Y macro in the Macro field of the Cue Stack window (use Page Right to find the Macro field). In the View Settings view of the Setup Window, set the Ethernet Remote Protocol to "ChamSys Rem tx".

The format of Ethernet commands is Y followed by the data. To send Ethernet data, the Y command must be the only macro command in the macro field. The Y command is followed by ASCII data contained within " " or ‘ ‘ or by decimal values separated by commas. For example to send Hello World followed by a carriage return:

Y"Hello World",10,13

To send the hexadecimal data stream 00 01 02 03 04

Y0,1,2,3,4

To send text only:

Y"abcedf"

To send several lines of text:

Y"Hello",10,13,"World",10,13

On the Ethernet the data above is encapsulated in the data field of ChamSys Ethernet Remote Protocol in the UDP packet.

Note that commas ‘,’ are not allowed within the ASCII data inside " " or ' ' . If you wish to send ', then you must send it as its hexadecimal ASCII code.

By default data received on the network is ignored. This can be changed to make MagicQ accept remote commands received on the network port. In Setup, View Settings, set the Ethernet Remote Protocol to "ChamSys Rem rx".

ChamSys Remote Protocol consists of simple commands consisting of a list parameter values separated by commas ', and ending in a character A to Z (or a to z). Commands can contain spaces, tabs, and carriage returns; they are all ignored. See the section on ChamSys Remote Protocol for further details.

The code fragments below show you could connect to MagicQ using simple C programming.

#define REMOTE_ETHER_PORT 0x1999
#define MAX_CREP_MSG 1000

typedef struct {
  long32 chamsys;
  word16 version;
  byte seq_fwd;
  byte seq_bkwd;
  word16 length;
  byte data;
} remote_ether_message_t;


int remote_ether_sock = 0;
word16 remote_ether_fwd = 0;
word16 remote_ether_bkwd = 0;


int remote_ether_init(void)
{
  struct sockaddr_in name;
  char opts[100];
  socklen_t optlen = 100;
  int flags;
  int i;

  // For Windows OS we need to start winsocket
#ifndef LINUX
  {
    WSAData ws;
    int code;
    code = WSAStartup(MAKEWORD(1,1),&ws);
  }
#endif

  if (remote_ether_sock)
    return (TRUE);

  remote_ether_sock = socket (PF_INET, SOCK_DGRAM, 0);
  getsockopt (remote_ether_sock,SOL_SOCKET,SO_REUSEADDR, opts, &optlen);
  opts[0] = 1;
  setsockopt (remote_ether_sock,SOL_SOCKET,SO_REUSEADDR, opts, optlen);

  /* Give the socket a name. */
  name.sin_family = AF_INET;
  name.sin_port = htons (REMOTE_ETHER_PORT);
  name.sin_addr.s_addr = htonl (INADDR_ANY);

  if (bind (remote_ether_sock, (struct sockaddr *) &name, sizeof (name)) <)
  {
    closesocket(remote_ether_sock);
    return (FALSE);
  }

  getsockopt (remote_ether_sock,SOL_SOCKET,SO_BROADCAST, opts, &optlen);
  opts[0] = 1;
  setsockopt (remote_ether_sock,SOL_SOCKET,SO_BROADCAST, opts, optlen);
  {
    u_long block;
    block = 1;
    ioctlsocket(remote_ether_sock,FIONBIO,&block);
  }

  return TRUE;
}

int remote_ether_rx(char *data, word16 size)
{
  char message[MAX_CREP_MSG];
  int nbytes;
  remote_ether_message_t *rem = (remote_ether_message_t *) message;
  struct sockaddr_in name;
  int name_len = sizeof(name);

  if (!remote_ether_sock) return (0);

  nbytes = recvfrom (remote_ether_sock,
                   message,
                   MAX_CREP_MSG,
                   0,
                   (struct sockaddr *) &name,
                   &name_len);

  if (nbytes > 0)
  {
    if (rem->chamsys == (('C'<<24)|('R'<<16)|('E'<<8)|('P')))
    {
      int len = wswap(rem->length);
      remote_ether_bkwd = rem->seq_fwd;

      if (len<(MAX_CREP_MSG-(sizeof(remote_ether_message_t)+1)))
      {
        if (len>size) len = size;
        memcpy(data,&(rem->data),len);
        return (len);
      }
    }
  }

  return (0);
}

char remote_ether_tx(char *data, word16 size)
{
  // Format the message
  byte message[MAX_CREP_MSG];
  remote_ether_message_t *rem = (remote_ether_message_t *) message;

  int nbytes;
  struct sockaddr_in name;

  if (!remote_ether_sock) return (FALSE);

  if (size>(MAX_CREP_MSG-sizeof(remote_ether_message_t)+1))
    size = MAX_CREP_MSG-sizeof(remote_ether_message_t)+1;

  rem->chamsys = (('C'<<24)|('R'<<16)|('E'<<8)|('P'));
  rem->version = wswap(0);
  rem->seq_fwd = remote_ether_fwd;
  rem->seq_bkwd = remote_ether_bkwd;
  rem->length = wswap(size);
  memcpy(&(rem->data),data,size);

  my_broadcast_address.s_addr = ip_address | ~subnet_address;
  name.sin_family = AF_INET;
  name.sin_port = htons (REMOTE_ETHER_PORT);
  name.sin_addr.s_addr = dwswap (my_broadcast_address.s_addr);

  nbytes = sendto (remote_ether_sock,
                 message,
                 size(sizeof(remote_ether_message_t)-1),
                 0,
                 (struct sockaddr *) & name, sizeof(name)
                );

  if (nbytes>0) remote_ether_fwd++;

  return (TRUE);
}