socket bad file descriptor - sockets

Question

I want to write a multi clients socket program,
but I get Bad file descriptor when the stage of accept.
How can I correct my code? Thanks!
Here is my code
http://codepad.org/q0N1jTgz
Thanks!
Here is my part of code!
while(1)
{
struct sockaddr_in client_addr;
int addrlen = sizeof(client_addr);
/*Accept*/
if(clientfd = accept(sockfd, (struct sockaddr *)&client_addr, (socklen_t*)&addrlen) < 0)
{
perror("Accpet Error");
close(sockfd);
exit(-1);
}
/*Fork process*/
if(child = fork() < 0)
{
perror("Fork Error");
close(sockfd);
exit(-1);
}
else if(child == 0)
{
int my_client = clientfd;
close(sockfd);
send(my_client, welcome, sizeof(welcome), 0);
while ((res = recv(my_client, buffer1, sizeof(buffer1), 0)) > 0)
{
string command(buffer1);
cout << "receive from client:" << command << ", " << res << " bytes\n";
memset(buffer1, '\0', sizeof(buffer1));
}
}
close(clientfd);
}

Answer 1

there are a few bugs in your code
first you need to use parentheses around the assignments for child and clientfd.
line 68 should be changed to
if((clientfd = accept(sockfd, (struct sockaddr *)&client_addr, (socklen_t*)&addrlen)) < 0)
and line 76 should be
if((child = fork()) < 0)
additionally you must return or exit() from the forked process since you have already closed the listening socket.
so add exit(0); or return 0; after line 94
I highly recommend you compile your code with warnings enabled, to catch the assignment problems early. e.g use the -Wall and -Wextra flags if you are using gcc or g++