accept function loop in thread c++ socket - c++

Question

I have 2 questions:
first - I try to connect one client to server each time. (the accept function is in thread) but the connection fail in accept - return always -1 (instead of zero).
the second question - how I can add timeout for to accepting client?
server.h
class Server{
public:
void open(int port, object&);
void startThreadOPeration();
void stop(){};
~Server();
private:
sockaddr_in address;
int socketfd;
Object* obj;
void startThread();
std::thread acceptClient;
};
server.cpp
void Server::open(int port,Object& obj) {
this->obj = &obj;
int socketfd = socket(AF_INET, SOCK_STREAM, 0);
if (socketfd == -1) {
throw "Could not create a socket";
}
this->socketfd = socketfd;
sockaddr_in address;
address.sin_family = AF_INET;
address.sin_addr.s_addr = INADDR_ANY;
address.sin_port = htons(port);
this->address = address;
if (bind(socketfd, (struct sockaddr *) &this->address, sizeof(this->address)) == -1) {
throw "Could not bind the socket to an IP";
}
if (listen(this->socketfd, 5) == -1) {
throw "Error during listening command";
} else {
std::cout<<"Server is now listening ..."<<std::endl;
}
startThread();
}
void Server::startThreadOPeration() {
while (!side_server::stop) {
// accepting a client
int client_socket = accept(this->socketfd, (struct sockaddr *) &this->address,
(socklen_t *) &this->address); // Return -1
if (client_socket == -1) {
throw "Error accepting client";
}
//do operation
}
void Server::startThread() {
acceptClient = std::thread(&Server::startThreadOPeration,this);
}
Server::~Server(){
close(this->socketfd);
if(acceptClient.joinable()){
this->acceptClient.join();
}
}
thank you for help!

Answer 1

accept() takes 3 parameters - a socket, a pointer to a socket address structure, and a pointer to a socklen_t containing the maximum length of the given socket address structure. On success, the socklen_t will be updated with the actual length of the socket structure.
Unfortunately, your code calls accept() with the address of the this->address variable in the 3rd parameter rather than the address of a valid socklen_t variable. Odds are good this causes this->address to contain what will appear to be complete nonsense when accept() updates what it thinks is a socklen_t but really isn't.
void Server::startThreadOPeration() {
while (!side_server::stop) {
// accepting a client
socklen_t len = sizeof(this->address); // max size of address structure
int client_socket = accept(this->socketfd,
(struct sockaddr *) &this->address,
&tlen); // supply valid max length
if (client_socket == -1) {
throw "Error accepting client";
}
//do operation
}
accept() doesn't do timeouts easily, but select() does:
void Server::startThreadOPeration() {
while (!side_server::stop) {
fd_set readfds;
struct timeval tv;
int result;
FD_ZERO(&readfds);
tv.tv_sec = timeout_s; // number of seconds to wait here
tv.tv_usec = timeout_us; // number of additional us to wait here
FD_SET(this->socketfd, &readfds);
result = select(this->socketfd + 1, &readfds, NULL, NULL, &tv);
if (result > 0)
{
// cheating a bit here since the only thing in readfds will be this->socketfd
// normally you should check what of many file descriptors is set.
socklen_t len = sizeof(this->address);
int client_socket = accept(this->socketfd,
(struct sockaddr *) &this->address,
&tlen); // supply valid max length
if (client_socket == -1) {
throw "Error accepting client";
}
//do operation
}
else
{
// handle any failure except timeout here
}
}
}