NDS2 Application Program Interface

This module defines the client interface to both versions of the Network Data Server (classic NDS and NDS2). It is based on the "daq_" function set originally defined by Alex Ivanov for the classic NDS. The C-functions provide a low level interface to the server. In general, these must be used to implement the client server protocol defined elsewhere, e.g. here. A new set of client functions maintain a list of channels to be requested, properly formats the NDS server commands and help retrieve the requested data.

The following code snippet demonstrates how to use the nds2 client:

 -- Initialize
 --
 int rc = daq_startup();
 if (rc) {
     printf("global initialization failed\n");
     return 1;
 }

 -- Connect to server
 --
 const char* server = "ldas-pcdev1.ligo.caltech.edu";
 int           port = 31200;
 daq_t daqd;
 rc = daq_connect(&daqd, server, port, nds_v2);
 if (rc) {
     printf("Connection failed with error: %s\n", daq_strerror(rc));
     return 2;
 }

 -- Specify channels
 --
 const char* channel[4] = {
     "H1:DMT-STRAIN",
     "L1:DMT-STRAIN",
     "V1:h16384Hz",
     0
 }

 int i;
 for (i=0; i<4; i++) {
     rc = daq_request_channel(&daqd, channel+i, 0, 0);
 }

 --  Request data
 --
 time_t start_gps = 876543210;
 time_t end_gps   = 876543366;
 time_t delta     = 32;
 rc = daq_request_data(&daqd, start_gps, end_gps, delta);
 if (rc) {
     printf("Data request failed with error: %s\n", daq_strerror(rc));
     return 3;
 }

 --  Read data blocks
 --
 time_t t;
 for (t=start_gps; t<end_gps; t+=delta) {
     rc = daq_recv_next(&daqd);
     if (rc) {
         printf("Receive data failed with error: %s\n", daq_strerror(rc));
         return 4;
     }

     --  Get data
     --
     chan_req_t* stat = daq_get_channel_status(&daqd, channel[1]);
     if (!stat || stat->status <= 0) break;

 }

 --  Disconnect from server
 --
 daq_disconnect(&daqd);

The API is subdivided into the following modules:

• NDS2 access functions. Access functions and control/status structures.
• Multi-threaded listener Listener thread (deprecated)
• NDS2 access error codes. Return codes used by the functions.
• Internal and obsolete interfaces. Internal and obsolete stuff.