How to pass struct object over socket using sendto() and rcvfrom() functions? - sockets

Question

There is the code i am trying to implement in a client/server model but segmentation fault error is coming..
server:
/* this is the structure i am trying to pass*/
struct pkt{
char data[1000];
int seqNo;
int checksum;
void make_pkt(int seq,char dat[1000],int check)
{
seqNo=seq;
strcpy(data,dat);
checksum=check;
}
};
the main part is
main() /* main */
{
port=client_addr.sin_port;
cout<<"port : "<<port;
pkt *rcv=new pkt;
do{
cout<<"a"<<endl;
cout<<"port : "<<port;
pkt *newpkt=new pkt;
char *buffer=new char [1000];
strcpy(buffer,"Hamza");
newpkt->make_pkt(1,buffer,2);
cout<<"aa"<<endl;
client_addr.sin_port=port;
cout<<"port 2 : "<<client_addr.sin_port<<endl;
sendto(sockfd,&newpkt,sizeof(struct pkt),0,(struct sockaddr *) &client_addr,sizeof(client_addr));
cout<<"aaa"<<endl;
recvfrom(sockfd,&rcv,sizeof(struct pkt),0,(struct sockaddr *)&client_addr,&leng);
cout<<"bb :"<<rcv->seqNo<<endl;
}while(rcv->seqNo!=1);
}
client:
struct pkt{
char data[1000];
int seqNo;
int checksum;
pkt()
{
strcpy(data," ");
seqNo=0;
timer=0;
checksum=0;
}
};
main()
{
pkt *newpkt=new pkt;
do{
cout<<"aa"<<endl;
pkt *rcvpkt=new pkt;
socklen_t lengt=sizeof(my_addr);
recvfrom(sockfd,&rcvpkt,sizeof(struct pkt),0,(struct sockaddr *)&my_addr,&lengt);
cout<<"aaa"<<endl;
cout<<"aaa"<<rcvpkt->data<<endl;
newpkt->seqNo=1;
sendto(sockfd,&newpkt,sizeof(struct pkt),0,(struct sockaddr *) &my_addr,sizeof(my_addr));
}while(newpkt->seqNo!=1);
}
please tell me whats the problem in this code..?

Answer 1

You are not passing the struct instances to sendto() and recvfrom() correctly. Your pkt variables are pointers so you need to get rid of the & operator when passing them. You also have memory leaks. Try this instead:
main()
{
port = ntohs(client_addr.sin_port);
cout << "port : " << port;
pkt *rcv = new pkt;
do{
cout << "a" << endl;
cout << "port : " << port;
pkt *newpkt = new pkt;
char buffer[1000];
strcpy(buffer,"Hamza");
newpkt->make_pkt(1,buffer,2);
cout << "aa" << endl;
client_addr.sin_port = htons(port);
cout << "port 2 : " << ntohs(client_addr.sin_port) << endl;
sendto(sockfd, newpkt, sizeof(struct pkt), 0, (struct sockaddr *) &client_addr, sizeof(client_addr));
delete newpkt;
cout << "aaa" << endl;
recvfrom(sockfd, rcv, sizeof(struct pkt), 0, (struct sockaddr *)&client_addr, &leng);
cout << "bb :" << rcv->seqNo << endl;
}
while(rcv->seqNo != 1);
delete rcv;
}
main()
{
pkt *newpkt = new pkt;
do{
cout << "aa" << endl;
pkt *rcvpkt = new pkt;
socklen_t lengt = sizeof(my_addr);
recvfrom(sockfd, rcvpkt, sizeof(struct pkt), 0, (struct sockaddr *)&my_addr, &lengt);
cout << "aaa" << endl;
cout << "aaa" << rcvpkt->data << endl;
newpkt->seqNo = 1;
sendto(sockfd, newpkt, sizeof(struct pkt), 0, (struct sockaddr *) &my_addr, sizeof(my_addr));
delete rcvpkt;
}
while(newpkt->seqNo != 1);
delete newpkt;
}