C++ Custom Client Handler - c++

Question

Below is the code that accepts a client... I just added a bit to add it to a pool which is a list<Client>. Client is my own class that is defined by (SOCKET, Char*) socket and ip address. The addclient2pool() function just adds to the list. Then I iterate through the list and send data via the stored socket in Client.
while(true) {
ClientSocket = accept(ListenSocket, (struct sockaddr *) &n, &len);
if (ClientSocket == INVALID_SOCKET) {
printf("accept failed with error: %d\n", WSAGetLastError());
closesocket(ListenSocket);
WSACleanup();
return;
}
addClient2Pool(Client(ListenSocket, inet_ntoa(n.sin_addr)));
}
The socket seems to have closed so I can't send messages... 10057. I am pretty sure there's something fundamentally wrong with the way I am storing the socket into Client class but I am new to C++.
void messageHandler() {
int iSend;
char* charB = "hello!";
while(true) {
for(ClientPool::iterator it = mainClientPool.begin(); it != mainClientPool.end(); ++it) {
Client c = *it;
SOCKET sock = c.getSocket();
iSend = send(sock, charB, sizeof(charB),0);
if (iSend == SOCKET_ERROR) {
printf("send failed with error: %d\n", WSAGetLastError());
}
}
Sleep(2000);
}
}
I used std::thread nameofthread(void) and nameofthread.join();

Answer 1

I see several issues with your code.
You are passing ListenSocket to Client() when you should be passing ClientSocket instead:
addClient2Pool(Client(ClientSocket, inet_ntoa(n.sin_addr)));
If you need to shut down the server for any reason, you should close any active client sockets first. In your example, if accept() fails, you are calling closesocket(ListenSocket) and WSACleanup() without clearing mainClientPool first (I assume your ~Client() deconstructor calls closesocket() on the client socket):
mainClientPool.clear(); // <-- add this
closesocket(ListenSocket);
WSACleanup();
When looping through your list, you need to use a Client& reference when deferencing the iterator so you are not making temporary copies of your Client objects that invoke their destructors when they go out of scope (thus closing your client sockets):
Client &c = *it; // <-- add '&'
You are misusing sizeof(). Since charB is a char* and not a char[], you need to use strlen() instead:
iSend = send(sock, charB, strlen(charB), 0);
Lastly, when send() (or any other socket operation) fails, you should close the failed client socket and remove it from your list. Which means changing your for() loop into a while() loop so you can modify the list while you are looping through it:
void messageHandler() {
...
while(true) {
...
ClientPool::iterator it = mainClientPool.begin();
while (it != mainClientPool.end()) {
...
if (iSend == SOCKET_ERROR) {
...
it = mainClientPool.erase(it);
} else {
++it;
}
}
...
}
...
}