Address family not supported by protocol UDP C Error sending - c

Question

I'm trying to implement communication by UDP protocol, and I'm getting an error: "Error sending: Address family not supported by protocol". I've checked in Google for this problem but couldn't managed to find answer.
Please be patient, I'm only starting my adventure with coding in C.
Here is a C code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <arpa/inet.h>
#define BUFLEN 512
// define function that deals with errors
void error(const char *msg)
{
perror(msg); // print error msg
exit(1); // exit the main() function
}
int main(int argc, char *argv[])
{
struct sockaddr_in serv1_addr, serv2_addr, cli1_addr, cli2_addr; //definicja struktur adresów servera i clienta
struct hostent *server; //defines host addres struct
int cl1_sockfd, se1_sockfd, se2_sockfd, i, c1len = sizeof(cli1_addr), c2len = sizeof(cli2_addr), recv_len, portno1,portno2; // creates inits
int cli1_len = sizeof(cli1_addr);
int cli2_len = sizeof(cli2_addr);
char buf[BUFLEN];
if (argc < 4) {
fprintf(stderr,"ERROR, no port provided\n"); // deal with wrong port
exit(1);
}
//tworzenie soceketu servera
if ((se1_sockfd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) == -1){
error("socket1"); //if socket() return -1 -- error
}
if ((se2_sockfd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) == -1){
error("socket2"); //if socket() return -1 -- error
}
//zero out the structure
memset( &serv1_addr, 0, sizeof(serv1_addr)); //put zero into structure
memset( &serv2_addr, 0, sizeof(serv2_addr)); //put zero into structure
portno1 = atoi(argv[2]); // get port number
portno2 = atoi(argv[3]);
serv1_addr.sin_family = AF_INET; // specify address family (IPv4)
serv1_addr.sin_addr.s_addr = inet_addr("127.0.0.1");
serv1_addr.sin_port = htons(portno1); // set port number
serv2_addr.sin_family = AF_INET; // specify address family (IPv4)
serv2_addr.sin_addr.s_addr = inet_addr("127.0.0.1");
serv2_addr.sin_port = htons(portno2); // set port number
if(connect(se1_sockfd,(struct sockaddr *) &serv1_addr, sizeof(serv1_addr)) < 0)
error ("ERROR connecting1"); //if connection failed
if(connect(se2_sockfd,(struct sockaddr *) &serv2_addr, sizeof(serv2_addr)) < 0)
error ("ERROR connecting2"); //if connection failed
while(1) //inf loop
{
printf("Please enter the message: "); //write the msg to socket
bzero(buf, 512); //fill buffer with zeros
fgets(buf, 512, stdin); //read into buffer
if( sendto( se1_sockfd, buf, BUFLEN, 0, (struct sockaddr*) &cli1_addr, cli1_len) < 0)
error ("Error sending1");
if( sendto( se2_sockfd, buf, BUFLEN, 0, (struct sockaddr*) &cli2_addr, cli2_len) < 0)
error ("Error sending2");
if (recvfrom(se1_sockfd, buf, BUFLEN, 0, (struct sockaddr *) &cli1_addr, &cli1_len) == -1){
error("recivfrom()1"); //if reciving failed -- error
}
printf("Data: %s\n", buf);
if (recvfrom(se2_sockfd, buf, BUFLEN, 0, (struct sockaddr *) &cli2_addr, &cli2_len) == -1){
error("recivfrom()2"); //if reciving failed -- error
}
printf("Data: %s\n", buf);
}
close(se1_sockfd);
close(se2_sockfd);
return 0;
}
Thanks for your help. ;)

Answer 1

Your issue is likely because of uninitialized destination address. sendto() takes destination address as the one before the last argument. But you are trying to provide not-initialized address (like for recvfrom())
if( sendto( se1_sockfd, buf, BUFLEN, 0, (struct sockaddr*) &cli1_addr, cli1_len) < 0)
error ("Error sending1");
^^^
Try serv1_addr instead ?
Also need to provide appropriate size.
One more thing. As long as you use sendto() - no need to perform connect(). UDP is connectionless and connect() only establishes default destination address for those who is going to use send() on such socket. But this is not your case because you provide destination address each time you call sendto(). Even more - you may use different addresses each time.
P.S. Reference: sendto()