windows api判断端口是否被占用

在Windows API中，可以使用`GetTcpTable()`函数和`GetUdpTable()`函数来获取当前系统中正在使用的TCP和UDP端口信息。通过遍历这些信息，可以判断指定的端口是否被占用。

以下是使用`GetTcpTable()`函数和`GetUdpTable()`函数判断指定端口是否被占用的示例代码：

#include <winsock2.h>
#include <iphlpapi.h>
#include <stdio.h>

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

bool IsPortInUse(USHORT port, bool isTCP)
{
    PMIB_TCPTABLE pTcpTable;
    PMIB_UDPTABLE pUdpTable;
    DWORD dwSize = 0;
    DWORD dwRetVal = 0;
    bool bInUse = false;

    if (isTCP)
    {
        pTcpTable = (PMIB_TCPTABLE)malloc(sizeof(MIB_TCPTABLE));
        if (pTcpTable == NULL)
        {
            printf("Error allocating memory\n");
            return false;
        }
        dwSize = sizeof(MIB_TCPTABLE);
        dwRetVal = GetTcpTable(pTcpTable, &dwSize, TRUE);
        if (dwRetVal == ERROR_INSUFFICIENT_BUFFER)
        {
            free(pTcpTable);
            pTcpTable = (PMIB_TCPTABLE)malloc(dwSize);
            if (pTcpTable == NULL)
            {
                printf("Error allocating memory\n");
                return false;
            }
            dwRetVal = GetTcpTable(pTcpTable, &dwSize, TRUE);
        }
        if (dwRetVal != NO_ERROR)
        {
            printf("GetTcpTable failed with error %d\n", dwRetVal);
            free(pTcpTable);
            return false;
        }
        for (DWORD i = 0; i < pTcpTable->dwNumEntries; i++)
        {
            if (pTcpTable->table[i].dwLocalPort == htons(port))
            {
                bInUse = true;
                break;
            }
        }
        free(pTcpTable);
    }
    else
    {
        pUdpTable = (PMIB_UDPTABLE)malloc(sizeof(MIB_UDPTABLE));
        if (pUdpTable == NULL)
        {
            printf("Error allocating memory\n");
            return false;
        }
        dwSize = sizeof(MIB_UDPTABLE);
        dwRetVal = GetUdpTable(pUdpTable, &dwSize, TRUE);
        if (dwRetVal == ERROR_INSUFFICIENT_BUFFER)
        {
            free(pUdpTable);
            pUdpTable = (PMIB_UDPTABLE)malloc(dwSize);
            if (pUdpTable == NULL)
            {
                printf("Error allocating memory\n");
                return false;
            }
            dwRetVal = GetUdpTable(pUdpTable, &dwSize, TRUE);
        }
        if (dwRetVal != NO_ERROR)
        {
            printf("GetUdpTable failed with error %d\n", dwRetVal);
            free(pUdpTable);
            return false;
        }
        for (DWORD i = 0; i < pUdpTable->dwNumEntries; i++)
        {
            if (pUdpTable->table[i].dwLocalPort == htons(port))
            {
                bInUse = true;
                break;
            }
        }
        free(pUdpTable);
    }

    return bInUse;
}

int main()
{
    USHORT port = 80;
    bool isTCP = true;

    if (IsPortInUse(port, isTCP))
    {
        printf("Port %d is in use\n", port);
    }
    else
    {
        printf("Port %d is not in use\n", port);
    }

    return 0;
}

在上面的示例代码中，`IsPortInUse()`函数用于判断指定的端口是否被占用，其中`port`参数为指定的端口号，`isTCP`参数表示是否为TCP端口。如果端口被占用，该函数返回`true`，否则返回`false`。