请教怎么检测局域网内某机器的TCP/UDP端口是否打开的呢

请问如何检测局域网内某机器的TCP/UDP端口是否打开的呢？
如题，TCP的端口我用一个TCPclient来Connect一下的笨办法实现了

那么UDP端口怎么弄呢？

------解决方案--------------------
你可以参考这个udp的扫描程序
/* http://www.cotse.com Fear the swimming Elephant! */

/* UDP scanner.
Please dont go around scanning the planet it isnt polite.

We try and identify open UDP ports by sending a bogus UDP packet
then waiting for an ICMP message of "PORT UNREACHABLE".

There are a few problems with this UDP scanner which I'll probably c0de up
to bypass. One bieng the fact that both ICMP and UDP get lost. I thought of
adding an RTT mechanism but that would be an overkill for a simple
example like this one. In the long run your better off using RTT if your
doing it in a congested network.

Since we're not using direct packet capturing on the
interace itself the kernel may or may not drop the packets before
passing them to all proccesses currently using SOCK_RAW and IPPROTO_ICMP.
A better implementation would use libpcap.

I honestly have no idea if its been done before in the same way.

Fri Sep 20 01:47:48 1996

Copyleft 1996 shadows@whitefang.com
shadows@kuwait.net

Has been tested on FreeBSD 2.1.5
*/
 
#include <stdlib.h>
#include <stdio.h>
#include <sys socket.h="">
#include <sys types.h="">
#include <sys time.h="">

#include <netinet in_systm.h="">
#include <netinet in.h="">
#include <netinet ip.h="">
#include <netinet ip_icmp.h="">
#include <arpa inet.h="">
#include <netdb.h>
#include <unistd.h>
#include <strings.h>
#include <errno.h>
 
/* Tweak these to make things faster. I've included getopt as well
since I'm an option kinda guy ;) */
 
#define MAXPACKET 4096
#define DEFAULT_TIMEOUT 10
#define DEFAULT_RESEND 6
#define SPORT 1
#define EPORT 1024
 
extern char *optarg;
extern int optind;
 
void usage(char *string)
{
fprintf(stderr,"usage: %s hostname|ipaddr [-s start port] [-e end port] [-t timeout]\n",string);
exit(-1);
}

void start_scanning(unsigned short sport,unsigned short eport,struct in_addr myaddr,unsigned short timeout,int maxretry)
{
struct sockaddr_in myudp;
char buff[] = "This was a blatant UDP port scan.";
int udpsock, rawsock, retry, retval,iplen;
unsigned short port;
fd_set r;
struct timeval mytimeout;
struct icmp *packet;
struct ip *iphdr;
struct servent *service;
unsigned char recvbuff[MAXPACKET];
 
if((udpsock = socket(AF_INET,SOCK_DGRAM,IPPROTO_UDP)) < 0)
{
perror("socket()");
exit(-1);
}
 
if((rawsock = socket(AF_INET,SOCK_RAW,IPPROTO_ICMP)) < 0)
{
perror("socket()");
exit(-1);
}
 
if(!(sport))
sport = SPORT;
if(!(eport))
eport = EPORT;
if(!(timeout))
timeout = DEFAULT_TIMEOUT;
if(!(maxretry))
maxretry = DEFAULT_RESEND;
 
if(sport > eport)
{
fprintf(stderr,"Uh you've got the start-port at %u and the end-port at %u this doesnt look right.\n",sport,eport);
exit(-1);
}
 
bcopy(&myaddr.s_addr,&myudp.sin_addr.s_addr,sizeof(myaddr.s_addr));
 
myudp.sin_family = AF_INET;

mytimeout.tv_sec = timeout;
mytimeout.tv_usec = 0;

for(port = sport;port < eport;port++)