Mail Archives: cygwin/2006/09/27/11:17:53
Hello,
I saw these series of posts on UDP - was there a conclusion to them?
http://cygwin.com/ml/cygwin/2006-06/msg00701.html
http://cygwin.com/ml/cygwin/2006-06/msg00703.html
http://cygwin.com/ml/cygwin/2006-06/msg00705.html
http://cygwin.com/ml/cygwin/2006-06/msg00706.html
I compile and run net-snmp under cygwin (I have net-snmp 5.3.0.1).
The server snmpd by default uses UDP port 161. I now have the most
recent cygwin DLL and the server snmpd seems no longer to work.
I think I tracked down the problem to the bind command. For a
"very simple test" I used Beej's socket programming examples.
I give the listings at the end of the message.
http://beej.us/guide/bgnet/output/htmlsingle/bgnet.html#listen
The listener program works fine on regular Linux and with older
cygwin DLLs ..... but under the latest it returns an error.
Has something changed?
Many Thanks,
Mark.
-----
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listener.c
====
/*
** listener.c -- a datagram sockets "server" demo
*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#define MYPORT 4950 // the port users will be connecting to
#define MAXBUFLEN 100
int main(void)
{
int sockfd;
struct sockaddr_in my_addr; // my address information
struct sockaddr_in their_addr; // connector's address information
socklen_t addr_len;
int numbytes;
char buf[MAXBUFLEN];
if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
perror("socket");
exit(1);
}
my_addr.sin_family = AF_INET; // host byte order
my_addr.sin_port = htons(MYPORT); // short, network byte order
my_addr.sin_addr.s_addr = INADDR_ANY; // automatically fill with my IP
memset(&(my_addr.sin_zero), '\0', 8); // zero the rest of the struct
if (bind(sockfd, (struct sockaddr *)&my_addr,
sizeof(struct sockaddr)) == -1) {
perror("bind");
exit(1);
}
addr_len = sizeof(struct sockaddr);
if ((numbytes = recvfrom(sockfd, buf, MAXBUFLEN-1 , 0,
(struct sockaddr *)&their_addr, &addr_len)) == -1) {
perror("recvfrom");
exit(1);
}
printf("got packet from %s\n",inet_ntoa(their_addr.sin_addr));
printf("packet is %d bytes long\n",numbytes);
buf[numbytes] = '\0';
printf("packet contains \"%s\"\n",buf);
close(sockfd);
return 0;
}
====
talker.c
====
/*
** talker.c -- a datagram "client" demo
*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#define SERVERPORT 4950 // the port users will be connecting to
int main(int argc, char *argv[])
{
int sockfd;
struct sockaddr_in their_addr; // connector's address information
struct hostent *he;
int numbytes;
if (argc != 3) {
fprintf(stderr,"usage: talker hostname message\n");
exit(1);
}
if ((he=gethostbyname(argv[1])) == NULL) { // get the host info
perror("gethostbyname");
exit(1);
}
if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
perror("socket");
exit(1);
}
their_addr.sin_family = AF_INET; // host byte order
their_addr.sin_port = htons(SERVERPORT); // short, network byte order
their_addr.sin_addr = *((struct in_addr *)he->h_addr);
memset(&(their_addr.sin_zero), '\0', 8); // zero the rest of the struct
if ((numbytes = sendto(sockfd, argv[2], strlen(argv[2]), 0,
(struct sockaddr *)&their_addr, sizeof(struct sockaddr))) == -1) {
perror("sendto");
exit(1);
}
printf("sent %d bytes to %s\n", numbytes, inet_ntoa(their_addr.sin_addr));
close(sockfd);
return 0;
}
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