connection error: Invalid argument at sockets - c++

Question

I have this code
Server:
//"sock" has already been created with no problem and binding as well
void Connection::bind_connection(int port){
cout << "Port " << port << endl;
server.sin_family = AF_INET ;
server.sin_addr.s_addr = htonl(INADDR_ANY);
server.sin_port = htons(port);
/* Bind socket to address */
struct sockaddr *serverptr = ( struct sockaddr *) &server;
if ( bind ( sock , serverptr , sizeof(server) ) < 0) {
perror("Binding error"); exit(BE);
}
cout << "Server binding completed!" << endl;
}
struct sockaddr_in client ;
socklen_t clientlen ;
struct sockaddr * clientptr =( struct sockaddr *) &client ;
if ( listen (sock , MAX_CONNECTIONS) < 0) {perror("listening error"); exit(LE);}
cout << "Listening for connections to port " << port << endl;
while (1) {
/* accept connection */
if (( newsock = accept ( sock , clientptr , &clientlen ) ) < 0) {
perror("Accepting error"); cout << "Errno = " << errno << endl; exit(AE);
}
//Code
....
}
and
Client:
//struct sockaddr_in server; <--- declared as data member of class "Connection"
//"sock" has already been created with no problem
void Connection::do_connect(){
struct sockaddr *serverptr = ( struct sockaddr *) &server;
if ( connect ( sock , serverptr , sizeof (server) ) < 0)
perror("client connect"); exit(CE);
cout << "Client connecting to the server" << endl;
}
and I get the above message. Most of the code is copied from the lesson slides but modified for my needs. Googling the problem it seems that I give wrong size at the syscall(s). Any idea where exactly the problem is? Thanks in advance.

Answer 1

Those lines always exit:
if ( connect ( sock , serverptr , sizeof (server) ) < 0)
perror("client connect"); exit(CE);
You might start to think about using a different indention scheme. Typically one that does not use more then one statement per line.
For the above code a tool like indent would have formatted it like this:
if (connect (sock, serverptr, sizeof (server)) < 0)
perror("client connect");
exit(CE);
This format makes the programming bug obvious.

Answer 2

You didn't initialize clientlen.
socklen_t clientlen = sizeof(client);
You can catch similar problems in future by running your code through valgrind.

Answer 3

As already indicated, you do not seem to be initializing your variables properly. You do not show how you initialize your sockaddr_in structures, which is likely the culprit. A relatively easy way to specify the address for bind() or connect() is to use getaddrinfo()/freeaddrinfo(). From the documentation:
Synopsis
int getaddrinfo(const char *node, const char *service,
const struct addrinfo *hints,
struct addrinfo **res);
void freeaddrinfo(struct addrinfo *res);
Description
Given node and service, which identify an Internet host and a service, getaddrinfo() returns one or more addrinfo structures, each of which contains an Internet address that can be specified in a call to bind(2) or connect(2). ...
The freeaddrinfo()function frees the memory that was allocated for the dynamically allocated linked list res.
As a simple example, here is a function that can connect to a server specified by a string that has the format <servername>:<port>:
int connect_tcp (std::string hostspec) {
struct addrinfo hints = { .ai_flags = AI_NUMERICSERV };
struct addrinfo *res = 0;
std::istringstream ss(hostspec);
std::string node, service;
int sock = -1;
std::getline(ss, node, ':');
std::getline(ss, service, ':');
getaddrinfo(node.c_str(), service.c_str(), &hints, &res);
for (struct addrinfo *rp = res; rp != 0; rp = rp->ai_next) {
if (rp->ai_socktype != SOCK_STREAM) continue;
int sock = socket(rp->ai_family, SOCK_STREAM, 0);
if (sock == -1) continue;
if (connect(sock, rp->ai_addr, rp->ai_addrlen) != -1)
break;
close(sock);
sock = -1;
}
freeaddrinfo(res);
if (sock == -1) errno = EHOSTDOWN;
return sock;
}