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udp socket functions with timeout

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This commit is contained in:
Heinz Junkes
2025-12-15 14:25:30 +01:00
committed by Andrew Johnson
parent 84d4627987
commit d3e414cbec
1 changed files with 26 additions and 23 deletions
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49
modules/libcom/RTEMS/epicsNtp.c
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@@ -2,6 +2,8 @@
* (C) 2014 David Lettier.
* http://www.lettier.com/
* SPDX-License-Identifier: BSD-3-Clause
*
* use of UDP funktions and implement timeout, HPJ 15.12.2025
\*************************************************************************/
#include <unistd.h>
@@ -20,7 +22,6 @@
int epicsNtpGetTime(char *ntpIp, struct timespec *now)
{
int sockfd, n; // Socket file descriptor and the n return result from writing/reading from the socket.
int portno = 123; // NTP UDP port number.
@@ -30,34 +31,31 @@ int epicsNtpGetTime(char *ntpIp, struct timespec *now)
// Set the first byte's bits to 00,011,011 for li = 0, vn = 3, and mode = 3. The rest will be left set to zero.
*( ( char * ) &packet + 0 ) = 0x1b; // Represents 27 in base 10 or 00011011 in base 2.
// Create a UDP socket, convert the host-name to an IP address, set the port number,
// connect to the server, send the packet, and then read in the return packet.
struct sockaddr_in serv_addr; // Server address data structure.
sockfd = socket( AF_INET, SOCK_DGRAM, IPPROTO_UDP ); // Create a UDP socket.
/* Create an UDP socket, use IP address of given nameserver, set the port number
struct sockaddr_in serv_addr; // Server address data structure.
add timout of 2 seconds
*/
struct sockaddr_in serv_addr = {
.sin_family = AF_INET,
.sin_addr.s_addr = inet_addr(ntpIp),
.sin_port = htons( portno ),
};
sockfd = socket( AF_INET, SOCK_DGRAM, 0 );
if ( sockfd < 0 ) {
perror( "epicsNtpGetTime creating socket" );
return -1;
}
// Zero out the server address structure.
memset( ( char* ) &serv_addr, 0, sizeof( serv_addr ) );
serv_addr.sin_family = AF_INET;
serv_addr.sin_addr.s_addr = inet_addr(ntpIp);
serv_addr.sin_port = htons( portno );
// Call up the server using its IP address and port number.
if ( connect( sockfd, ( struct sockaddr * ) &serv_addr, sizeof( serv_addr) ) < 0 ) {
perror( "epicsNtpGetTime connecting socket" );
close( sockfd );
/* Set receive timeout to 2 seconds */
struct timeval tv = { .tv_sec = 2, .tv_usec = 0 };
if (setsockopt(sockfd, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv)) < 0) {
perror("setsockopt");
return -1;
}
// Send it the NTP packet it wants. If n == -1, it failed.
n = write( sockfd, ( char* ) &packet, sizeof( ntp_packet ) );
n = sendto(sockfd, ( char* ) &packet, sizeof( ntp_packet ), 0, (struct sockaddr *)&serv_addr, sizeof(serv_addr));
if ( n < 0 ) {
perror( "epicsNtpGetTime sending NTP request" );
close( sockfd );
@@ -65,13 +63,18 @@ int epicsNtpGetTime(char *ntpIp, struct timespec *now)
}
// Wait and receive the packet back from the server. If n == -1, it failed.
n = read( sockfd, ( char* ) &packet, sizeof( ntp_packet ) );
if ( n < 0 ) {
perror( "epicsNtpGetTime reading NTP reply" );
n = recvfrom(sockfd, ( char* ) &packet, sizeof( ntp_packet ), 0, NULL, NULL);
if (n < 0) {
if (errno == EAGAIN || errno == EWOULDBLOCK) {
printf("Timeout - no response\n");
} else {
perror( "epicsNtpGetTime reading NTP reply" );
}
close( sockfd );
return -1;
} else {
printf("Received %zd bytes\n", n);
}
close( sockfd );
// These two fields contain the time-stamp seconds as the packet left the NTP server.