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/* net_dgpsip.c -- gather and dispatch DGPS data from DGPSIP servers
*
* This file is Copyright (c) 2010 by the GPSD project
* BSD terms apply: see the file COPYING in the distribution root for details.
*/
#include <sys/types.h>
#include <stdio.h>
#include <stdbool.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#ifndef S_SPLINT_S
#include <netdb.h>
#include <sys/socket.h>
#include <unistd.h>
#endif /* S_SPLINT_S */
#include "gpsd.h"
/*@ -branchstate */
int dgpsip_open(struct gps_context_t *context, const char *dgpsserver)
/* open a connection to a DGPSIP server */
{
char hn[256], buf[BUFSIZ];
char *colon, *dgpsport = "rtcm-sc104";
int opts;
if ((colon = strchr(dgpsserver, ':')) != NULL) {
dgpsport = colon + 1;
*colon = '\0';
}
if (!getservbyname(dgpsport, "tcp"))
dgpsport = DEFAULT_RTCM_PORT;
context->dsock =
netlib_connectsock(AF_UNSPEC, dgpsserver, dgpsport, "tcp");
if (context->dsock >= 0) {
gpsd_report(LOG_PROG, "connection to DGPS server %s established.\n",
dgpsserver);
(void)gethostname(hn, sizeof(hn));
/* greeting required by some RTCM104 servers; others will ignore it */
(void)snprintf(buf, sizeof(buf), "HELO %s gpsd %s\r\nR\r\n", hn,
VERSION);
if (write(context->dsock, buf, strlen(buf)) == (ssize_t) strlen(buf))
context->netgnss_service = netgnss_dgpsip;
else
gpsd_report(LOG_ERROR, "hello to DGPS server %s failed\n",
dgpsserver);
} else
gpsd_report(LOG_ERROR,
"can't connect to DGPS server %s, netlib error %d.\n",
dgpsserver, context->dsock);
opts = fcntl(context->dsock, F_GETFL);
if (opts >= 0)
(void)fcntl(context->dsock, F_SETFL, opts | O_NONBLOCK);
return context->dsock;
}
/*@ +branchstate */
void dgpsip_report(struct gps_device_t *session)
/* may be time to ship a usage report to the DGPSIP server */
{
/*
* 10 is an arbitrary number, the point is to have gotten several good
* fixes before reporting usage to our DGPSIP server.
*/
if (session->context->fixcnt > 10 && !session->context->sentdgps) {
session->context->sentdgps = true;
if (session->context->dsock > -1) {
char buf[BUFSIZ];
(void)snprintf(buf, sizeof(buf), "R %0.8f %0.8f %0.2f\r\n",
session->gpsdata.fix.latitude,
session->gpsdata.fix.longitude,
session->gpsdata.fix.altitude);
if (write(session->context->dsock, buf, strlen(buf)) ==
(ssize_t) strlen(buf))
gpsd_report(LOG_IO, "=> dgps %s\n", buf);
else
gpsd_report(LOG_IO, "write to dgps FAILED\n");
}
}
}
#define DGPS_THRESHOLD 1600000 /* max. useful dist. from DGPS server (m) */
#define SERVER_SAMPLE 12 /* # of servers within threshold to check */
struct dgps_server_t
{
double lat, lon;
char server[257];
double dist;
};
static int srvcmp(const void *s, const void *t)
{
return (int)(((const struct dgps_server_t *)s)->dist - ((const struct dgps_server_t *)t)->dist); /* fixes: warning: cast discards qualifiers from pointer target type */
}
void dgpsip_autoconnect(struct gps_context_t *context,
double lat, double lon, const char *serverlist)
/* tell the library to talk to the nearest DGPSIP server */
{
struct dgps_server_t keep[SERVER_SAMPLE], hold, *sp, *tp;
char buf[BUFSIZ];
FILE *sfp = fopen(serverlist, "r");
if (sfp == NULL) {
gpsd_report(LOG_ERROR, "no DGPS server list found.\n");
context->dsock = -2; /* don't try this again */
return;
}
for (sp = keep; sp < keep + SERVER_SAMPLE; sp++) {
sp->dist = DGPS_THRESHOLD;
sp->server[0] = '\0';
}
/*@ -usedef @*/
while (fgets(buf, (int)sizeof(buf), sfp)) {
char *cp = strchr(buf, '#');
if (cp != NULL)
*cp = '\0';
if (sscanf(buf, "%lf %lf %256s", &hold.lat, &hold.lon, hold.server) ==
3) {
hold.dist = earth_distance(lat, lon, hold.lat, hold.lon);
tp = NULL;
/*
* The idea here is to look for a server in the sample array
* that is (a) closer than the one we're checking, and (b)
* furtherest away of all those that are closer. Replace it.
* In this way we end up with the closest possible set.
*/
for (sp = keep; sp < keep + SERVER_SAMPLE; sp++)
if (hold.dist < sp->dist
&& (tp == NULL || hold.dist > tp->dist))
tp = sp;
if (tp != NULL)
memcpy(tp, &hold, sizeof(struct dgps_server_t));
}
}
(void)fclose(sfp);
if (keep[0].server[0] == '\0') {
gpsd_report(LOG_ERROR, "no DGPS servers within %dm.\n",
(int)(DGPS_THRESHOLD / 1000));
context->dsock = -2; /* don't try this again */
return;
}
/*@ +usedef @*/
/* sort them and try the closest first */
qsort((void *)keep, SERVER_SAMPLE, sizeof(struct dgps_server_t), srvcmp);
for (sp = keep; sp < keep + SERVER_SAMPLE; sp++) {
if (sp->server[0] != '\0') {
gpsd_report(LOG_INF, "%s is %dkm away.\n", sp->server,
(int)(sp->dist / 1000));
if (dgpsip_open(context, sp->server) >= 0)
break;
}
}
}
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