how to perform ssdp communicationbetween upnp devices - udp

Question

i am trying to implement the upnp level communication between the devices .. but facing problem in getting the response message .and more over on sending the ssdp:discovery multicast not able to recieve the messages from the devices ... please guide me through i am completely newto this topic
pre-requisite done by me :
1.able to send the M-Search ..and notify message on the network .. and have confirmed via wireshark
2.gone through the upnp architecture related pdf
response got in wireshark :
when ever i am sending the message i am getting the icmp error message that destination is not reachable ..
< client side code > is the first one and second one is the for time being i am just sending up the data on local host
#include <arpa/inet.h>
#include <netinet/in.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <unistd.h>
#define SRV_IP "127.0.0.1"
/* diep(), #includes and #defines like in the server */
#define BUFLEN 512
#define NPACK 10
#define PORT 1900
void diep(char *s)
{
perror(s);
exit(1);
}
int main(void)
{
struct sockaddr_in si_other;
int s, i, slen=sizeof(si_other);
char buf[BUFLEN];
if ((s=socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP))==-1)
diep("socket");
memset((char *) &si_other, 0, sizeof(si_other));
si_other.sin_family = AF_INET;
si_other.sin_port = htons(PORT);
if (inet_aton(SRV_IP, &si_other.sin_addr)==0) {
fprintf(stderr, "inet_aton() failed\n");
exit(1);
}
for (i=0; i<NPACK; i++) {
printf("Sending packet %d\n", i);
sprintf(buf, "\n");
if (sendto(s, buf, BUFLEN, 0, &si_other, slen)==-1)
diep("sendto()");
}
close(s);
return 0;
}
#include <arpa/inet.h>
#include <netinet/in.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <unistd.h>
#define BUFLEN 512
#define NPACK 10
#define PORT 1900
void diep(char *s)
{
perror(s);
exit(1);
}
int main(void)
{
struct sockaddr_in si_me, si_other;
int s, i, slen=sizeof(si_other);
char buf[BUFLEN];
if ((s=socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP))==-1)
diep("socket");
memset((char *) &si_me, 0, sizeof(si_me));
si_me.sin_family = AF_INET;
si_me.sin_port = htons(PORT);
si_me.sin_addr.s_addr = htonl(INADDR_ANY);
if (bind(s, &si_me, sizeof(si_me))==-1)
diep("bind");
for (i=0; i<NPACK; i++) {
if (recvfrom(s, buf, BUFLEN, 0, &si_other, &slen)==-1)
diep("recvfrom()");
printf("Received packet from %s:%d\nData: %s\n\n",
inet_ntoa(si_other.sin_addr), ntohs(si_other.sin_port), buf);
}
close(s);
return 0;
}

Answer 1

The individual lines in you M-SEARCH need to have "\r\n" at the end of each line, not just a "\n". Your system may just be sending "\n" across the wire. Check the bytes you're sending for a 13 followed by a 10. That's "\r\n".