c++ - Winsock API - 在两个线程中同时发送和接收数据
问题描述
我正在尝试在同一个程序中构建客户端和服务器。例如,用户 1 向用户 2 发送了一个数据包,用户 2 收到数据包后向用户 1 发送了一个不同的数据包。问题是,运行程序后,用户都没有收到数据包。如果我将客户端构建在将程序与其工作的服务器分开
#pragma comment(lib,"ws2_32.lib")
#include <WinSock2.h>
#include <iostream>
#include <thread>
static const int num_threads = 2;
static char buffer[8096 + 1];
char a[256] = {};
char MOTD[256];
void call_from_thread(int tid) {
// ---------- Server code: ---------- //
if( tid == 0 ){
WSAData wsaData;
WORD DllVersion = MAKEWORD(2, 1);
if (WSAStartup(DllVersion, &wsaData) != 0){MessageBoxA(NULL, "WinSock startup failed", "Error", MB_OK | MB_ICONERROR);}
SOCKADDR_IN addr;
int addrlen = sizeof(addr);
addr.sin_addr.s_addr = inet_addr("127.0.0.1");
addr.sin_port = htons(1112);
addr.sin_family = AF_INET;
SOCKET sListen = socket(AF_INET, SOCK_STREAM, NULL);
bind(sListen, (SOCKADDR*)&addr, sizeof(addr));
listen(sListen, SOMAXCONN);
SOCKET newConnection;
newConnection = accept(sListen, (SOCKADDR*)&addr, &addrlen);
if (newConnection == 0){
std::cout << "Failed to accept the client's connection." << std::endl;
}else{
std::cout << "Client Connected!" << std::endl;
}
while (true){
std::cin >> a;
send(newConnection, a, sizeof(a), NULL);
}
}else if( tid == 1 ){
// ---------- Client code: ---------- //
WSAData wsaData;
WORD DllVersion = MAKEWORD(2, 1);
if (WSAStartup(DllVersion, &wsaData) != 0){MessageBoxA(NULL, "Winsock startup failed", "Error", MB_OK | MB_ICONERROR);}
SOCKADDR_IN addr;
int sizeofaddr = sizeof(addr);
addr.sin_addr.s_addr = inet_addr("127.0.0.1");
addr.sin_port = htons(1111);
addr.sin_family = AF_INET;
SOCKET Connection = socket(AF_INET, SOCK_STREAM, NULL); //Set Connection socket
if (connect(Connection, (SOCKADDR*)&addr, sizeofaddr) != 0) //If we are unable to connect...
{
MessageBoxA(NULL, "Failed to Connect", "Error", MB_OK | MB_ICONERROR);
//return 0; //Failed to Connect
}
std::cout << "Connected!" << std::endl;
char MOTD[256];
while (true){
recv(Connection, MOTD, sizeof(MOTD), NULL); //Receive Message of the Day buffer into MOTD array
std::cout << "MOTD:" << MOTD << std::endl;
}
}
// ---------- Thread selection: ---------- //
int main() {
std::thread t[num_threads];
for (int i = 0; i < num_threads; ++i) {
t[i] = std::thread(call_from_thread, i);
}
for (int i = 0; i < num_threads; ++i) {
t[i].join();
}
}
解决方案
服务器正在监听 1112 端口,但客户端正在连接到 1111 端口。这意味着客户端和服务器根本不可能相互连接,无论它们是否在同一个应用程序中。
我还看到您的代码存在许多其他问题,包括:
WSAStartup()
应该在应用程序启动时调用一次,而不是每个线程。如果任何 WinSock 函数失败,则两个线程都不会完全退出。
客户端线程不会等待服务器线程打开其侦听端口,然后客户端才能连接到它。
潜在的缓冲区溢出。
资源泄露。
缺乏体面的错误处理。
- 在服务器端,您完全忽略了
socket()
、bind()
、listen()
和报告的错误send()
,并且您没有accept()
正确检查 的返回值。 - 在客户端,您完全忽略了
socket()
and报告的错误recv()
。而且,在将MOTD
缓冲区打印到std::cout
.
- 在服务器端,您完全忽略了
尝试更多类似的东西:
#include <winsock2.h>
#include <windows.h>
#pragma comment(lib,"ws2_32.lib")
#include <iostream>
#include <thread>
#include <string>
#include <cstdint>
#include <stdexcept>
#include <limits>
#include <algorithm>
// The below variables are used to let the client wait for the server
// port to be opened. If you don't want to use these, especially if the
// client and server are ever run on different machines, you can omit
// these and instead just have the client call connect() in a loop
// until successful...
//
#include <mutex>
#include <condition_variable>
#include <chrono>
static std::condition_variable server_cv;
static std::mutex server_mtx;
static bool server_is_listening = false;
//
static const int num_threads = 2;
static const u_short server_port = 1111;
class winsock_error : public std::runtime_error
{
public:
int errCode;
std::string funcName;
winsock_error(int errCode, const char *funcName) : std::runtime_error("WinSock error"), errCode(errCode), funcName(funcName) {}
};
void WinSockError(const char *funcName, int errCode = WSAGetLastError())
{
throw winsock_error(errCode, funcName);
}
class connection_closed : public std::runtime_error
{
public:
connection_closed() : std::runtime_error("Connection closed") {}
};
class socket_ptr
{
public:
socket_ptr(SOCKET s) : m_sckt(s) {}
socket_ptr(const socket_ptr &) = delete;
socket_ptr(socket_ptr &&src) : m_sckt(src.m_sckt) { src.m_sckt = INVALID_SOCKET; }
~socket_ptr() { if (m_sckt != INVALID_SOCKET) closesocket(m_sckt); }
socket_ptr& operator=(const socket_ptr &) = delete;
socket_ptr& operator=(socket_ptr &&rhs) { m_sckt = rhs.m_sckt; rhs.m_sckt = INVALID_SOCKET; return *this; }
operator SOCKET() { return m_sckt; }
bool operator!() const { return (m_sckt == INVALID_SOCKET); }
private:
SOCKET m_sckt;
}
template <typename T>
T LimitBufferSize(size_t size)
{
return (T) std::min(size, (size_t) std::numeric_limits<T>::max());
}
void sendRaw(SOCKET sckt, const void *buffer, size_t buflen)
{
const char *ptr = static_cast<const char*>(buffer);
while (buflen > 0)
{
int numToSend = LimitBufferSize<int>(buflen);
int numSent = ::send(sckt, ptr, numToSend, 0);
if (numSent == SOCKET_ERROR)
WinSockError("send");
ptr += numSent;
buflen -= numSent;
}
}
void recvRaw(SOCKET sckt, void *buffer, size_t buflen)
{
char *ptr = static_cast<char*>(buffer);
while (buflen > 0)
{
int numToRecv = LimitBufferSize<int>(buflen);
int numRecvd = ::recv(sckt, ptr, numToRecv, 0);
if (numRecvd == SOCKET_ERROR)
WinSockError("recv");
if (numRecvd == 0)
throw connection_closed();
ptr += numRecvd;
buflen -= numRecvd;
}
}
void sendStr(SOCKET sckt, const std::string &str)
{
uint32_t len = LimitBufferSize<uint32_t>(str.size());
uint32_t tmp = htonl(len);
sendRaw(sckt, &tmp, sizeof(tmp));
if (len > 0)
sendRaw(sckt, str.c_str(), len);
}
std::string recvStr(SOCKET sckt)
{
std::string str;
uint32_t len;
recvRaw(sckt, &len, sizeof(len));
len = ntohl(len);
if (len > 0)
{
str.resize(len);
recvRaw(sckt, &str[0], len);
}
return str;
}
void server_thread()
{
std::cout << "[Server] Starting ..." << std::endl;
try
{
socket_ptr sListen(::socket(AF_INET, SOCK_STREAM, IPPROTO_TCP));
if (!sListen)
WinSockError("socket");
SOCKADDR_IN addr = {};
addr.sin_family = AF_INET;
addr.sin_addr.s_addr = ::inet_addr("127.0.0.1");
addr.sin_port = ::htons(server_port);
int addrlen = sizeof(addr);
if (::bind(sListen, (SOCKADDR*)&addr, sizeof(addr)) == SOCKET_ERROR)
WinSockError("bind");
if (::listen(sListen, 1) == SOCKET_ERROR)
WinSockError("listen");
// this is optional...
{
std::unique_lock<std::mutex> lk(server_mtx);
server_is_listening = true;
}
server_cv.notify_all();
//
std::cout << "[Server] Listening for Client ..." << std::endl;
socket_ptr newConnection(::accept(sListen, (SOCKADDR*)&addr, &addrlen));
if (!newConnection)
WinSockError("accept");
std::cout << "[Server] Client Connected!" << std::endl;
try
{
std::string a;
while (std::cin >> a)
sendStr(newConnection, a);
}
catch (const connection_closed &)
{
}
catch (const winsock_error &e)
{
std::cerr << "[Server] Client error: " << e.errCode << " on WinSock function: " << e.funcName << std::endl;
}
std::cout << "[Server] Client Disconnected!" << std::endl;
}
catch (const winsock_error &e)
{
std::cerr << "[Server] Error: " << e.errCode << " on WinSock function: " << e.funcName << std::endl;
}
catch (const std::exception &e)
{
std::cerr << "[Server] Unexpected Error! " << e.what() << std::endl;
}
std::cout << "[Server] Stopped!" << std::endl;
}
void client_thread()
{
std::cout << "[Client] Starting ..." << std::endl;
try
{
// this is optional, could call connect() below in a loop instead...
std::cout << "[Client] Waiting for Server ..." << std::endl;
{
std::unique_lock<std::mutex> lk(server_mtx);
if (!server_cv.wait_for(lk, std::chrono::seconds(5), []{ return server_is_listening; }))
throw std::runtime_error("Server not listening after 5 seconds!");
}
//
socket_ptr sConnection(::socket(AF_INET, SOCK_STREAM, IPPROTO_TCP));
if (!sConnection)
WinSockError("socket");
SOCKADDR_IN addr = {};
addr.sin_family = AF_INET;
addr.sin_addr.s_addr = ::inet_addr("127.0.0.1");
addr.sin_port = ::htons(server_port);
if (::connect(sConnection, (SOCKADDR*)&addr, sizeof(addr)) == SOCKET_ERROR)
WinSockError("connect");
std::cout << "[Client] Connected!" << std::endl;
try
{
std::string MOTD;
while (true)
{
MOTD = recvStr(sConnection);
std::cout << "[Client] MOTD: " << MOTD << std::endl;
}
}
catch (const connection_closed &)
{
}
catch (const winsock_error &e)
{
std::cerr << "[Client] Server error: " << e.errCode << " on WinSock function: " << e.funcName << std::endl;
}
std::cout << "[Client] Disconnected!" << std::endl;
}
catch (const winsock_error &e)
{
std::cerr << "[Client] Error: " << e.errCode << " on WinSock function: " << e.funcName << std::endl;
}
catch (const std::exception &e)
{
std::cerr << "[Client] Unexpected Error! " << e.what() << std::endl;
}
std::cout << "[Client] Stopped!" << std::endl;
}
int main()
{
WSADATA wsaData;
int ret = ::WSAStartup(MAKEWORD(2, 1), &wsaData);
if (ret != 0)
{
std::cerr << "WinSock Startup failed with error: " << ret << std::endl;
return -1;
}
std::cout << "WinSock Startup successful" << std::endl;
std::thread t[num_threads];
t[0] = std::thread(server_thread);
t[1] = std::thread(client_thread);
for (int i = 0; i < num_threads; ++i) {
t[i].join();
}
::WSACleanup();
return 0;
}
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