求LINUX下的端口扫描程序
使用Socket API，接受IP 地址，输出该IP 地址对应的主机所支持的<端口号, 协议(TCP/UDP), 服务名[3]>

[解决办法]
开源的 nmap ...
[解决办法]

以前调试过一个，发个你看下吧。
其实道理不难，就是发送icmp包，跟ping类似，然后等待回应，若超时或者无响应则判断端口未开。
主机扫描的也类似。

#include<stdio.h>

#include<stdlib.h>

#include<string.h>

#include<math.h>

#include<netdb.h>
#include<unistd.h>
#include<sys/time.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in_systm.h>
#include<netinet/in.h>
#include<netinet/ip.h>
#include<netinet/ip_icmp.h>
#include<arpa/inet.h>
#include <time.h>


/*#define CHKADDRESS( _saddr_)
{
   u_char *p =(char *)&(_saddr_);
   if( (p[0] == 10) 
[解决办法]
 (p[0] ==168 &&16<=p[1]&&p[1]<=31) 
[解决办法]
(p[0] ==192 && p[1]==168)
   {}
   else
   {

fprintf(stderr,"IP address error.\n");
exit(EXIT_FAILURE);
   }
}*/

enum {CMD_NAME,DST_IP,START_PORT,LAST_PORT};

#define MAXBUFF 8192

int main(int argc,char *argv[])
{
  clock_t start, finish;  
  struct icmp *icmp;
  fd_set select_fd;
  struct sockaddr_in send_sa;
  int recv_sd;
  int send_sd;
  char buff[MAXBUFF];
  int endport;
  int startport;
  int dstport;
  struct timeval tv;
  struct ip *ip;
  int hlen,port;
  int count;

  if(argc!=4)
  {
fprintf(stderr," usge:%s dst_ip start_port last_port\n",argv[CMD_NAME]);
exit(EXIT_FAILURE);
  }
  send_sa.sin_family = AF_INET;
  send_sa.sin_addr.s_addr = inet_addr(argv[DST_IP]);

  startport = atoi(argv[START_PORT]);
  endport = atoi(argv[LAST_PORT]);
  //CHKADDRESS(send_sa.sin_addr.s_addr);
  
  if( (send_sd = socket(AF_INET,SOCK_DGRAM,0))<0)
  {
perror(" socket (SOCK_DGRAM)");
exit(EXIT_FAILURE);
  }

  if( (recv_sd = socket(AF_INET,SOCK_RAW,IPPROTO_ICMP))<0)
  {
perror(" socket (SOCK_RAW)");
exit(EXIT_FAILURE);
  }

  for(dstport = startport;dstport<=endport;dstport++)
  {
printf(" Scan port %d: %d times\r",dstport,count);
        fflush(stdout);
  send_sa.sin_port = htons (dstport);
sendto(send_sd,NULL,0,0,(void *) &send_sa,sizeof(send_sa));
   
tv.tv_sec=1;
tv.tv_usec=0;
count=0;                   //记录每次同一端口,ICMP包数量 
 
start = clock();  

while(1)
{
FD_ZERO(&select_fd);
FD_SET(recv_sd,&select_fd);

if(select (recv_sd+1,&select_fd,NULL,NULL,&tv)>0) 
if(recvfrom(recv_sd,buff,MAXBUFF,0,NULL,NULL)!=56)          //ICMP包,长度为56,IP+ICMP+IP+UDP
continue;
//intf("a new icmp ack\n");
if( ((finish=clock() )-start)>=2)
{
printf("2 sec no target icmp ack.\n");
struct servent *se_t;
se_t=getservbyport(htons (dstport)," udp");
printf("%5d %-20s\n",dstport,(se_t==NULL)?"unkown":se_t->s_name);
break;
}
ip=(struct ip *)buff;
hlen=ip->ip_hl<<2;
icmp=(struct icmp *)(buff+hlen);

port=ntohs(* (u_short *)(buff+20+8+20+2) );
if( (ip->ip_src.s_addr!=send_sa.sin_addr.s_addr) 
[解决办法]
 (icmp->icmp_type!=ICMP_UNREACH) 
[解决办法]
 (icmp->icmp_code!=ICMP_UNREACH_PORT) 
[解决办法]
(port!=dstport))
{
if(count>10)
{
printf("port %d:icmp_type is %d;icmp_code is %d.\n",port,icmp->icmp_type,icmp->icmp_code);
break;
}
if(ip->ip_src.s_addr==send_sa.sin_addr.s_addr && port==dstport)
{
//printf(" %d times\r",count);
count++;
break;
}
//printf("Not target icmp packet.continue check port %d\n",dstport);
continue;
}
else
{
struct servent *se;
se=getservbyport(htons (dstport)," udp");
//if(se!=NULL)
printf("%5d %-20s\n",dstport,(se==NULL)?"unkown":se->s_name);
}
break;
}
  }
  return EXIT_SUCCESS;
}

[解决办法]
[root@RHEL4_U5 ~]# netstat -a
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address Foreign Address State
tcp 0 0 *:ftp *:* LISTEN
tcp 0 0 *:ssh *:* LISTEN
getnameinfo failed
getnameinfo failed
tcp 0 0 [UNKNOWN]:ssh [UNKNOWN]:2341 ESTABLISHED

Active UNIX domain sockets (servers and established)
Proto RefCnt Flags Type State I-Node Path
unix 4 [ ] DGRAM 5684 /dev/log
unix 2 [ ACC ] STREAM LISTENING 5895 /var/run/acpid.socket
unix 2 [ ACC ] STREAM LISTENING 6133 /tmp/.font-unix/fs7100
unix 2 [ ACC ] STREAM LISTENING 6106 /var/run/iiim/.iiimp-unix/9010
unix 2 [ ACC ] STREAM LISTENING 6169 /var/run/dbus/system_bus_socket
unix 2 [ ] DGRAM 6358 @/var/run/hal/hotplug_socket
unix 2 [ ] DGRAM 3840 @udevd
unix 2 [ ] DGRAM 14405
unix 3 [ ] STREAM CONNECTED 6357 /var/run/dbus/system_bus_socket
unix 3 [ ] STREAM CONNECTED 6356
unix 3 [ ] STREAM CONNECTED 6177
unix 3 [ ] STREAM CONNECTED 6176
unix 2 [ ] DGRAM 6028
unix 3 [ ] STREAM CONNECTED 5795
unix 3 [ ] STREAM CONNECTED 5794
unix 2 [ ] DGRAM 5703
[root@RHEL4_U5 ~]#