谁能帮我改一下 这个 简单的端口扫描器

这几天要做网络课设，但是自己又不会编程  网上下了个代码 自己研究了半天 看不懂

不明白为什么这程序只输出前面的部分，后面的都没执行

#include <winsock.h>  这个也没看懂

课设的题目是：

简单的端口扫描器
实现一个端口扫描程序,判断指定的主机有哪些端口可以提供服务, 并把扫描得知的结果记录下来


下面是代码   各位热心的帮忙看看 改改

#include <string.h>
#include <winsock.h>
#include <windows.h>
#include <iostream.h>
#pragma comment (lib,"ws2_32.lib")
int main (int argc, char *argv[])
{
    int iportFrom,iportTo;
    int testsocket;
    int iopenedport = 0;
    struct sockaddr_in target_addr;
    WSADATA wsaData;
    WORD wVersionRequested=MAKEWORD(1,1);
    if (argc <= 3)
    {
        cout << "使用格式 : " << argv[0] << " 主机IP地址 开始端口号 结束端口号\n" << endl;
        exit(1);
    }
    if (atoi (argv[2]) > atoi (argv[3]))
    {
        cout << "错误！开始端口号必须小于结束端口号" << endl;
        exit(1);
    }
    else
    {
        if (WSAStartup (wVersionRequested , &wsaData) )
        {
            cout << "连接socket库失败，请检查版本号是否为1.1\n" << endl;
            exit(1);
        }
        iportFrom=atoi (argv[2]);
        iportTo=atoi (argv[3]);
        for (int i=iportFrom; i <= iportTo; i++)
        {
            cout << "正在建立socket................................" << endl;
            if ((testsocket=socket (AF_INET,SOCK_STREAM,0) ) == INVALID_SOCKET)
            {
                cout << "Socket建立失败！" << endl;
                exit(0);
            }
            target_addr.sin_family = AF_INET;
            target_addr.sin_port = htons(i);
            target_addr.sin_addr.s_addr = inet_addr (argv[1]);
            cout << "正在扫描端口：" << i << endl;
            if (connect (testsocket, (struct sockaddr *) &target_addr, sizeof(struct sockaddr)) == SOCKET_ERROR)
                cout << "端口" << i << "关闭！" << endl;
            else
            {
                iopenedport++;
                cout << "端口" << i << "开放\n" << endl;
            }
        }
        cout << "目标主机" << argv[1] << "从" << iportFrom << "--" << iportTo << "共有" << iopenedport << "个端口开放" << endl;
        closesocket (testsocket);
        WSACleanup();
    }
    return 0;
}