C++利用Winsock bind检测本机端口是否被占用的操作方法

WSADATA wsa;
if (WSAStartup(MAKEWORD(2, 2), &wsa) != 0)
{
    return false;
}
bool available = false;
SOCKET s = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
if (s != INVALID_SOCKET)
{
    sockaddr_in addr{};
    addr.sin_family = AF_INET;
    addr.sin_port = htons((u_short)port);
    addr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
    available = (bind(s, reinterpret_cast<sockaddr*>(&addr), sizeof(addr)) == 0);
    closesocket(s);
}
WSACleanup();
return available;

flowchart TD
    A[开始：输入端口号] --> B[WSAStartup 初始化 Winsock]
    B -->|失败| E1[返回 Error 并携带错误码]
    B -->|成功| C[创建 TCP socket]
    C -->|INVALID_SOCKET| E2[返回 Error 并携带错误码]
    C -->|成功| D[bind 127.0.0.1:port]
    D -->|返回 0| F[端口可用 Available]
    D -->|SOCKET_ERROR| G[WSAGetLastError]
    G -->|WSAEADDRINUSE 或 WSAEACCES| H[端口不可用 InUse]
    G -->|其他错误| E3[返回 Error 并携带错误码]
    F --> Z[closesocket + WSACleanup]
    H --> Z
    E2 --> Z
    E1 --> Z2[结束]
    Z --> Z2

// 在 bind 之前调用，要求 _WIN32_WINNT >= 0x0501（VS2019/2022 默认满足）
BOOL exclusive = TRUE;
setsockopt(s, SOL_SOCKET, SO_EXCLUSIVEADDRUSE,
           reinterpret_cast<const char*>(&exclusive), sizeof(exclusive));

#include <winsock2.h>
#include <iostream>
#include <cstdint>

#pragma comment(lib, "ws2_32.lib")

// 端口探测结果
enum class PortStatus
{
    Available,   // 端口可用（未被占用）
    InUse,       // 端口已被占用 / 被系统保留
    Error,       // 探测过程出错（Winsock 初始化失败等）
};

// 探测端口是否可用，outError 用于回传 WSAGetLastError 的值
PortStatus IsPortAvailable(uint16_t port, int* outError = nullptr)
{
    WSADATA wsa{};
    if (WSAStartup(MAKEWORD(2, 2), &wsa) != 0)
    {
        if (outError) *outError = WSAGetLastError();
        return PortStatus::Error;
    }

    PortStatus status = PortStatus::Available;
    SOCKET s = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (s == INVALID_SOCKET)
    {
        status = PortStatus::Error;
        if (outError) *outError = WSAGetLastError();
    }
    else
    {
        // 想探测"能否以任意地址绑定"，把 INADDR_LOOPBACK 换成 INADDR_ANY 即可
        sockaddr_in addr{};
        addr.sin_family = AF_INET;
        addr.sin_port = htons(port);
        addr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);

        // 可选：提高可靠性，防止与设置了 SO_REUSEADDR 的 socket 共存造成假阳性
        // BOOL exclusive = TRUE;
        // setsockopt(s, SOL_SOCKET, SO_EXCLUSIVEADDRUSE,
        //            reinterpret_cast<const char*>(&exclusive), sizeof(exclusive));

        if (bind(s, reinterpret_cast<sockaddr*>(&addr), sizeof(addr)) == SOCKET_ERROR)
        {
            const int err = WSAGetLastError();
            if (outError) *outError = err;
            // 这两种错误码都代表"端口不可用"，其余视为系统级错误
            status = (err == WSAEADDRINUSE || err == WSAEACCES)
                         ? PortStatus::InUse
                         : PortStatus::Error;
        }
        closesocket(s);
    }

    WSACleanup();
    return status;
}

int main()
{
    constexpr uint16_t port = 8080;
    int err = 0;
    switch (IsPortAvailable(port, &err))
    {
    case PortStatus::Available:
        std::cout << "端口 " << port << " 可用" << std::endl;
        break;
    case PortStatus::InUse:
        std::cout << "端口 " << port << " 不可用，WSAError=" << err << std::endl;
        break;
    case PortStatus::Error:
        std::cout << "探测出错，WSAError=" << err << std::endl;
        break;
    }
    return 0;
}

#include <winsock2.h>
#include <iphlpapi.h>
#include <vector>
#include <cstdint>

#pragma comment(lib, "ws2_32.lib")
#pragma comment(lib, "Iphlpapi.lib")

// 返回所有监听在指定端口上的进程 PID（IPv4）
std::vector<DWORD> GetPidsListeningOnPort(uint16_t port)
{
    std::vector<DWORD> pids;
    DWORD size = 0;

    // 第一次调用用于获取所需缓冲区大小
    if (GetExtendedTcpTable(nullptr, &size, FALSE, AF_INET,
                            TCP_TABLE_OWNER_PID_LISTENER, 0) != ERROR_INSUFFICIENT_BUFFER)
        return pids;

    std::vector<BYTE> buf(size);
    if (GetExtendedTcpTable(buf.data(), &size, FALSE, AF_INET,
                            TCP_TABLE_OWNER_PID_LISTENER, 0) != NO_ERROR)
        return pids;

    const auto* table = reinterpret_cast<const MIB_TCPTABLE_OWNER_PID*>(buf.data());
    for (DWORD i = 0; i < table->dwNumEntries; ++i)
    {
        const auto& row = table->table[i];
        // 注意：dwLocalPort 是网络字节序，需转换后再比较
        if (ntohs(static_cast<u_short>(row.dwLocalPort)) == port)
            pids.push_back(row.dwOwningPid);
    }
    return pids;
}

netsh interface ipv4 show excludedportrange protocol=tcp