TCP掃描器的簡單實現

//TcpPortScanner.cc
#include <iostream>
#include <strings.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
using namespace std;

int main(int argc, char *argv[])
{
    int fromport = atoi(argv[2]);
    int toport = atoi(argv[3]);
    if(fromport > toport)
    {
    int temp;
    temp = fromport;
    fromport = toport;
    toport = temp;
    }

    for(int i = fromport; i < toport; i++)
    {
    int sk = socket(AF_INET, SOCK_STREAM, 0);

    struct sockaddr_in server;
    bzero(&server, sizeof(server));
    server.sin_family = AF_INET;
    server.sin_port = htons(i);
    server.sin_addr.s_addr = inet_addr(argv[1]);

    if(connect(sk, (struct sockaddr*)&server, sizeof(server)) == 0)
    {
        cout << argv[1] << "開放了端口：" << i << endl;
    }

    close(sk);
    }

    return 0;
}

套接字socket（即sk）要在for循環裏面創建，如果在for循環外面創建則第一次connect函數成功之後，sk並沒有關閉，不能用來連接其他的端口，則下次的connect連接就會失敗，所有隻會掃描出一個開了的端口。