Segmentation fault sending a struct through TCP socket - c++

Question

I'm writing a simple program about TCP Socket. What I'm going to do is send whatever 1000 data structure from client to server, but it display segmentation fault....
This is my server:
#include <iostream>
#include <string>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <stdlib.h>
#include <strings.h>
#include <stdio.h>
using namespace std;
#pragma pack(1)
struct student
{
int id;
string name;
};
main()
{
struct sockaddr_in socketInfo;
socklen_t fromlen;
int socketHandle;
int portNumber = 8080;
bzero(&socketInfo, sizeof(sockaddr_in)); // Clear structure memory
// create socket
if((socketHandle = socket(AF_INET, SOCK_STREAM, 0)) < 0)
{
close(socketHandle);
exit(EXIT_FAILURE);
}
// Load system information into socket data structures
socketInfo.sin_family = AF_INET; //IPv4
socketInfo.sin_addr.s_addr = htonl(INADDR_ANY); // Use any address available to the system
socketInfo.sin_port = htons(portNumber); // Set port number
// Bind the socket to a local socket address
if( bind(socketHandle, (struct sockaddr *) &socketInfo, sizeof(socketInfo)) < 0)
{
close(socketHandle);
perror("bind");
exit(EXIT_FAILURE);
}
listen(socketHandle, 1);
int socketConnection;
while(1)
{
cout<<"Waiting to connect ..."<<endl;
if( (socketConnection = accept(socketHandle, NULL, NULL)) < 0)
{
cout<<"Fail!!"<<endl;
exit(EXIT_FAILURE);
}
//close(socketHandle);
int rc = 0; // Actual number of bytes read
struct student buf;
while(1)
{
rc = recv(socketConnection, &buf, sizeof(struct student)+1, 0);
cout<<"Recieve = "<<rc<<endl;
if (rc<=0)
break;
cout<<buf.id<<endl;
cout<<buf.name<<endl;
}
}
}
This is my client:
#include <iostream>
#include <sstream>
#include <string>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <stdlib.h>
#include <errno.h>
#include <netinet/in.h>
#include <arpa/inet.h>
using namespace std;
unsigned long inet_addr(const string a);
string int2str( int val ) // interger convert to string
{
ostringstream out;
out<<val;
return out.str();
}
#pragma pack(1)
struct student
{
int id;
string name;
};
main()
{
struct sockaddr_in remoteSocketInfo;
struct hostent *hPtr;
const char *remoteHost="localhost";
int socketHandle;
int portNumber = 8080;
bzero(&remoteSocketInfo, sizeof(sockaddr_in)); // Clear structure memory
if((hPtr = gethostbyname(remoteHost)) == NULL)
{
cerr << "System DNS name resolution not configured properly." << endl;
cerr << "Error number: " << ECONNREFUSED << endl;
exit(EXIT_FAILURE);
}
if((socketHandle = socket(AF_INET, SOCK_STREAM, 0)) < 0)
{
close(socketHandle);
exit(EXIT_FAILURE);
}
// Load system information into socket data structures
memcpy((char *)&remoteSocketInfo.sin_addr, hPtr->h_addr, hPtr->h_length);
remoteSocketInfo.sin_family = AF_INET;
remoteSocketInfo.sin_port = htons(portNumber); // Set port number
if(connect(socketHandle, (struct sockaddr *)&remoteSocketInfo, sizeof(sockaddr_in)) < 0)
{
close(socketHandle);
exit(EXIT_FAILURE);
}
struct student buf[1000];
for (int i=0; i<1000; i++)
{
buf[i].id = i+1;
buf[i].name = "student_" + int2str(i) + "00";
send(socketHandle, &buf[i], sizeof(struct student)+1, 0);
}
}
Result:
Waiting to connect ...
Recieve = 13
1
Segmentation fault (core dumped)

Answer 1

The problem here is that one of the fields in struct student is a std::string object. This can't be sent across the wire directly like you're doing.
Instead, either change it to a fixed-size character array something like this...
struct student
{
int id;
char name[100];
}
... and write your name into there. Or you'll have to send it across the wire in a different way.