C++ TCP Server (Winsock) Connecting (invalid client) Instantly Then Closes - c++

Question

Edit: Working on a solution - turns out googling 204.204.204.204 gets me further than more descriptive requests.
Honestly. Wits end. I have no idea how I can spend an entire day doing something that took 10 minutes in Flask (Server) and Javascript (client). I need this to run in C++ and allow a client to connect via BlueStacks' port on the same machine. The client is unimportant because I can't even get that far.
I've tried WinSocks, I've tried WxWidget's networking implementation, I've even tried some random C++ wrapper thing. All of them failed (typically within the EXAMPLE! As in, copy paste and errors everywhere). So I ultimately went back to WinSockets and followed a tutorial on YouTube.
int ServerStuff() {
WSADATA WsData;
WORD ver = MAKEWORD(2, 2);
int wsOK = WSAStartup(ver, &WsData);
if (wsOK != 0) {
wxLogMessage("Can't initialize Winsock! Quitting");
return false;
}
//Create a socket
SOCKET listening = socket(AF_INET, SOCK_STREAM, 0);
if (listening == INVALID_SOCKET) {
wxLogMessage("Can't create a socket! Quitting");
return false;
}
//Bind the ip and port to a socket
sockaddr_in hint;
hint.sin_family = AF_INET;
hint.sin_port = htons(54000);
hint.sin_addr.S_un.S_addr = INADDR_ANY; //Could also use inet_pton
bind(listening, (sockaddr*)&hint, sizeof(hint));
//Tell winsock the socket is for listening
listen(listening, SOMAXCONN);
//Wait for a connection
sockaddr_in client;
int clientSize = sizeof(client);
SOCKET clientSocket = accept(listening, (sockaddr*)&client, &clientSize);
//if (clientSocket == INVALID_SOCKET) {
// wxLogMessage("Client Invalid Socket");
// return false;
//}
char host[NI_MAXHOST]; //Client's remote name
char service[NI_MAXHOST]; //Service (port) the client is connected on
ZeroMemory(host, NI_MAXHOST);
ZeroMemory(service, NI_MAXHOST);
if (getnameinfo((sockaddr*)&client, sizeof(client), host, NI_MAXHOST, service, NI_MAXSERV, 0) == 0) {
wxLogMessage("Can't initialize Winsock! Quitting");
}
else {
inet_ntop(AF_INET, &client.sin_addr, host, NI_MAXHOST);
wxLogMessage(host);
int wut = client.sin_port;
wxString mystring = wxString::Format(wxT("%i"), wut);
wxLogMessage("Connected on port");
wxLogMessage(mystring);
//wxLogMessage(to_string(ntohs(client.sin_port)));
}
wxLogMessage("Got this far somehow");
//Close listening socket - we don't need it anymore - later on we'll learn how to accept multiple client
closesocket(listening);
//while loop: accept and echo message back to client
char buf[4096];
while (true)
{
ZeroMemory(buf, 4096);
//Wait for client to send data
int bytesReceived = recv(clientSocket, buf, 4096, 0);
if (bytesReceived == SOCKET_ERROR) {
//wxLogMessage("ERROR in recv");
break;
}
if (bytesReceived == 0) {
wxLogMessage("Client Disconnected");
break;
}
//Echo back to client
send(clientSocket, buf, bytesReceived + 1, 0);
//Close the socket
closesocket(clientSocket);
//Cleanup winsock
WSACleanup();
wxLogMessage("Welp");
}
}
// event handlers
void MyFrame::OnQuit(wxCommandEvent& WXUNUSED(event))
{
// true is to force the frame to close
ServerStuff();
//Close(true);
}
On the YouTube video ("Creating a TCP Server in C++" - not allowed to post links) this works! The command window opens, is blank infinitely until he connects a client and then the client sends a message and the server replies with the same exact message in return.
Not mine. Mine just rushes through everything and then closes. My log used to immediately quit on the commented code where it states the client socket is invalid so I commented it out. Now my output is:
204.204.204.204
Connected on port
52428
Got this far somehow
I don't know what to do. I'm just trying to send data over a same-machine TCP connection. I'm baffled as to how this is so difficult. It seems like some random process is immediately trying to connect as a client to my server ? But why is it allowed to connect on port 52428 when I'm explicitly hosting on 54000?
My goal:
Start Server
Connect to Server using a Java App within BlueStacks
Send data from Server to Client
It makes more sense for the computer to be the server because there will be multiple BlueStacks instances and I'd prefer to not have to "spawn" multiple programs / servers for what I'm doing.

Answer 1

I see a few mistakes in your socket code.
not calling WSACleanup() if WSAStartup() is successful and then something goes wrong afterwards.
not calling closesocket() if socket() is successful and then something goes wrong afterwards.
not zeroing out the sockaddr_in that you pass to bind(). Random bytes in the struct can cause bind() to fail.
ignoring the return values of bind(), listen(), accept(), and send().
not treating the return value of getnameinfo() correctly. It returns 0 on success, not failure.
sending +1 extra byte back to the client than you received from the client. If the client sends fewer bytes than your buffer can hold, that extra byte would be 0x00 due to your ZeroMemory() call. But if the client actually sends enough bytes to completely fill your buffer, then you would send an extra byte from memory that you do not own. If you really want to send a null terminator after everything you echo, do so explicitly. Otherwise, a true echo server should only send back exactly what it receives, no more, no less.
Try something more like this:
void ServerStuff() {
WSADATA WsData;
int ret = WSAStartup(MAKEWORD(2, 2), &WsData);
if (ret != 0) {
wxLogMessage("Can't initialize Winsock! Error: %d", ret);
return;
}
//Create a socket
SOCKET listening = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
if (listening == INVALID_SOCKET) {
wxLogMessage("Can't create a socket! Error: %d", WSAGetLastError());
WSACleanup();
return;
}
//Bind the ip and port to a socket
sockaddr_in hint = {};
hint.sin_family = AF_INET;
hint.sin_port = htons(54000);
hint.sin_addr.s_addr = INADDR_ANY; //Could also use inet_pton
ret = bind(listening, (sockaddr*)&hint, sizeof(hint));
if (ret == SOCKET_ERROR) {
wxLogMessage("Can't bind socket! Error: %d", WSAGetLastError());
closesocket(listening);
WSACleanup();
return;
}
//Tell winsock the socket is for listening
ret = listen(listening, SOMAXCONN);
if (ret == SOCKET_ERROR) {
wxLogMessage("Can't listen on socket! Error: %d", WSAGetLastError());
closesocket(listening);
WSACleanup();
return;
}
//Wait for a connection
sockaddr_in client = {};
int clientSize = sizeof(client);
SOCKET clientSocket = accept(listening, (sockaddr*)&client, &clientSize);
if (clientSocket == INVALID_SOCKET) {
wxLogMessage("Can't accept a client! Error: %d", WSAGetLastError());
closesocket(listening);
WSACleanup();
return;
}
char host[NI_MAXHOST] = {}; //Client's remote name
ret = getnameinfo((sockaddr*)&client, sizeof(client), host, NI_MAXHOST, NULL, 0, 0);
if (ret != 0) {
wxLogMessage("Can't get client name info! Error: %d", ret);
inet_ntop(AF_INET, &(client.sin_addr), host, NI_MAXHOST);
}
wxLogMessage("Client: %s, Connected on port: %hu", host, ntohs(client.sin_port));
//Close listening socket - we don't need it anymore - later on we'll learn how to accept multiple client
closesocket(listening);
//while loop: accept and echo message back to client
char buf[4096];
int bytesReceived;
while (true)
{
//Wait for client to send data
bytesReceived = recv(clientSocket, buf, sizeof(buf), 0);
if (bytesReceived == SOCKET_ERROR) {
wxLogMessage("Can't read from client! Error: ", WSAGetLastError());
break;
}
if (bytesReceived == 0) {
wxLogMessage("Client Disconnected");
break;
}
//Echo back to client
ret = send(clientSocket, buf, bytesReceived, 0);
if (ret == SOCKET_ERROR) {
wxLogMessage("Can't send to client! Error: ", WSAGetLastError());
break;
}
}
//Close the socket
closesocket(clientSocket);
//Cleanup winsock
WSACleanup();
wxLogMessage("Welp");
}