【发布时间】：2021-05-09 08:35:19
【问题描述】：
我最近开始学习 c++，并且正在学习一些教程。我正在研究套接字，我决定作为一个附带项目来创建一个小型多线程服务器，如下所示。
我试图在达到CLIENTS_MAX_NUM 后关闭服务器侦听套接字，然后在套接字断开连接后重新打开它，但是这给了我一个错误 10022 (WSAEINVAL)，我不太确定我做错了什么.
如果您想重现错误，只需使用 telnet 连接并关闭客户端连接（ctrl+] ，退出）。
任何帮助将不胜感激。
#include <iostream>
#include <vector>
#include <string>
#include <future>
#include <chrono>
#include <WS2tcpip.h>
#pragma comment(lib, "ws2_32.lib")
static constexpr const unsigned int PORT = 5000;
static constexpr const unsigned int CLIENTS_MAX_NUM = 1;
static constexpr const unsigned int CLIENTS_QUEUE_NUM = 10;
SOCKET server_sock;
std::vector<std::future<void>> futures;
std::mutex mtx;
void initialize_winsock() {
WSAData wsData;
WORD ver = MAKEWORD(2, 2);
int wsResult = WSAStartup(ver, &wsData);
if (wsResult != 0) {
std::cerr << WSAGetLastError() << std::endl;
WSACleanup();
exit(EXIT_FAILURE);
}
}
void bind_server_socket() {
int keep_alive = 1;
int re_use = 1;
if (setsockopt(server_sock, SOL_SOCKET, SO_KEEPALIVE, (const char*)&keep_alive, sizeof(keep_alive)) == SOCKET_ERROR) {
closesocket(server_sock);
WSACleanup();
exit(EXIT_FAILURE);
}
if (setsockopt(server_sock, SOL_SOCKET, SO_REUSEADDR, (const char*)&re_use, sizeof(re_use)) == SOCKET_ERROR) {
closesocket(server_sock);
WSACleanup();
exit(EXIT_FAILURE);
}
sockaddr_in server;
server.sin_family = AF_INET;
server.sin_port = htons(PORT);
server.sin_addr.S_un.S_addr = INADDR_ANY;
memset(&server.sin_zero, 0, 8);
if (bind(server_sock, (sockaddr*)&server, sizeof(sockaddr)) == SOCKET_ERROR) {
std::cerr << WSAGetLastError() << std::endl;
closesocket(server_sock);
WSACleanup();
exit(EXIT_FAILURE);
}
}
void open_server_socket(bool &listening) {
server_sock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
if (server_sock == INVALID_SOCKET) {
std::cerr << WSAGetLastError() << std::endl;
listening = false;
WSACleanup();
exit(EXIT_FAILURE);
}
listening = true;
}
void close_server_socket(bool &listening) {
closesocket(server_sock);
listening = false;
}
void handle_client(SOCKET client_sock, sockaddr_in client) {
char buf[4096];
char host[NI_MAXHOST];
char service[NI_MAXHOST];
memset(host, 0, NI_MAXHOST);
memset(service, 0, NI_MAXHOST);
//std::cout << std::this_thread::get_id() << std::endl;
if (getnameinfo((sockaddr*)&client, sizeof(client), host, NI_MAXHOST, service, NI_MAXSERV, 0) == 0) {
std::cout << host << " connected on port " << service << std::endl;
}
else {
inet_ntop(AF_INET, &client.sin_addr, host, NI_MAXHOST);
std::cout << host << " connected on port " << ntohs(client.sin_port) << std::endl;
}
while (true) {
memset(&buf, 0, 4096);
const int bytes_received = recv(client_sock, buf, 4096, 0);
if (bytes_received == SOCKET_ERROR) {
std::cerr << WSAGetLastError() << std::endl;
WSACleanup();
}
else if (bytes_received == 0) {
std::cout << "client disconnected" << std::endl;
break;
}
else {
send(client_sock, buf, bytes_received + 1, 0);
}
}
}
int main(int argc, const char* argv[]) {
bool listening = false;
initialize_winsock();
open_server_socket(listening);
bind_server_socket();
// -----------------------------------------------------------
if (listen(server_sock, CLIENTS_QUEUE_NUM) == SOCKET_ERROR) {
std::cerr << WSAGetLastError() << std::endl;
closesocket(server_sock);
WSACleanup();
exit(EXIT_FAILURE);
}
else {
std::cout << "listening for incoming connections on port " << PORT << std::endl;
while (true) {
unsigned int removed = 0;
for (int i = 0; i < futures.size(); i++) {
auto status = futures.at(i).wait_for(std::chrono::milliseconds(0));
if (status == std::future_status::ready) {
futures.erase(futures.begin() + i);
removed++;
}
}
if (removed > 1) {
std::cout << removed << " clients removed" << std::endl;
}
else if (removed) {
std::cout << removed << " client removed" << std::endl;
}
if (futures.size() < CLIENTS_MAX_NUM && !listening) {
std::cout << "re-opening server socket" << std::endl;
open_server_socket(listening);
// BOOM <--- 10022 (WSAEINVAL) - https://docs.microsoft.com/en-us/windows/win32/winsock/windows-sockets-error-codes-2
}
if (listening) {
sockaddr_in client;
memset(&client.sin_zero, 0, 8);
int client_size = sizeof(client);
SOCKET client_sock = accept(server_sock, (sockaddr*)&client, &client_size);
if (client_sock == INVALID_SOCKET) {
std::cerr << WSAGetLastError() << std::endl;
closesocket(server_sock);
WSACleanup();
exit(EXIT_FAILURE);
}
else {
futures.emplace_back(std::async(std::launch::async, &handle_client, client_sock, client));
if (futures.size() >= CLIENTS_MAX_NUM && listening) {
std::cout << "closing server socket" << std::endl;
close_server_socket(listening);
}
std::cout << futures.size() << " clients connected" << std::endl;
}
}
}
}
// ----------------------------------------------------------
std::cout << "bye!" << std::endl;
WSACleanup();
exit(EXIT_SUCCESS);
}
【问题讨论】：
-
具体是什么给了你这个错误？关闭？重开？或者下次您使用重新打开但未重新绑定的服务器套接字调用 accept 时？
-
当我尝试重新打开套接字行号 211（注释所在的位置）时。我也尝试在重新打开后调用
bind_server_socket，但出现同样的错误。所以我猜它是别的东西？
标签： c++ multithreading sockets winsock2