Apr
26
2009

Packet Sniffer Code in C using Linux Sockets (BSD)

An article by Binary Tides

To code a sniffer in C (Linux) the steps would be :

1. Create a Raw Socket.
2. Put it in a recvfrom loop.

A raw socket when put in recvfrom receives all incoming packets. The following code shows an example of such a sniffer. Note that it sniffs only incoming packets. For sniffing all traffic on a network a packet capture library like libpcap can be used.

Code : sniffer.c

#include<stdio.h>	//For standard things
#include<stdlib.h>	//malloc
#include<string.h>	//memset
#include<netinet/ip_icmp.h>	//Provides declarations for icmp header
#include<netinet/udp.h>	//Provides declarations for udp header
#include<netinet/tcp.h>	//Provides declarations for tcp header
#include<netinet/ip.h>	//Provides declarations for ip header
#include<sys/socket.h>
#include<arpa/inet.h>

void ProcessPacket(unsigned char* , int);
void print_ip_header(unsigned char* , int);
void print_tcp_packet(unsigned char* , int);
void print_udp_packet(unsigned char * , int);
void print_icmp_packet(unsigned char* , int);
void PrintData (unsigned char* , int);

int sock_raw;
FILE *logfile;
int tcp=0,udp=0,icmp=0,others=0,igmp=0,total=0,i,j;
struct sockaddr_in source,dest;

int main()
{
	int saddr_size , data_size;
	struct sockaddr saddr;
	struct in_addr in;

	unsigned char *buffer = (unsigned char *)malloc(65536); //Its Big!

	logfile=fopen("log.txt","w");
	if(logfile==NULL) printf("Unable to create file.");
	printf("Starting...\n");
	//Create a raw socket that shall sniff
	sock_raw = socket(AF_INET , SOCK_RAW , IPPROTO_TCP);
	if(sock_raw < 0)
	{
		printf("Socket Error\n");
		return 1;
	}
	while(1)
	{
		saddr_size = sizeof saddr;
		//Receive a packet
		data_size = recvfrom(sock_raw , buffer , 65536 , 0 , &saddr , &saddr_size);
		if(data_size <0 )
		{
			printf("Recvfrom error , failed to get packets\n");
			return 1;
		}
		//Now process the packet
		ProcessPacket(buffer , data_size);
	}
	close(sock_raw);
	printf("Finished");
	return 0;
}

void ProcessPacket(unsigned char* buffer, int size)
{
	//Get the IP Header part of this packet
	struct iphdr *iph = (struct iphdr*)buffer;
	++total;
	switch (iph->protocol) //Check the Protocol and do accordingly...
	{
		case 1:  //ICMP Protocol
			++icmp;
			//PrintIcmpPacket(Buffer,Size);
			break;

		case 2:  //IGMP Protocol
			++igmp;
			break;

		case 6:  //TCP Protocol
			++tcp;
			print_tcp_packet(buffer , size);
			break;

		case 17: //UDP Protocol
			++udp;
			print_udp_packet(buffer , size);
			break;

		default: //Some Other Protocol like ARP etc.
			++others;
			break;
	}
	printf("TCP : %d   UDP : %d   ICMP : %d   IGMP : %d   Others : %d   Total : %d\r",tcp,udp,icmp,igmp,others,total);
}

void print_ip_header(unsigned char* Buffer, int Size)
{
	unsigned short iphdrlen;

	struct iphdr *iph = (struct iphdr *)Buffer;
	iphdrlen =iph->ihl*4;

	memset(&source, 0, sizeof(source));
	source.sin_addr.s_addr = iph->saddr;

	memset(&dest, 0, sizeof(dest));
	dest.sin_addr.s_addr = iph->daddr;

	fprintf(logfile,"\n");
	fprintf(logfile,"IP Header\n");
	fprintf(logfile,"   |-IP Version        : %d\n",(unsigned int)iph->version);
	fprintf(logfile,"   |-IP Header Length  : %d DWORDS or %d Bytes\n",(unsigned int)iph->ihl,((unsigned int)(iph->ihl))*4);
	fprintf(logfile,"   |-Type Of Service   : %d\n",(unsigned int)iph->tos);
	fprintf(logfile,"   |-IP Total Length   : %d  Bytes(Size of Packet)\n",ntohs(iph->tot_len));
	fprintf(logfile,"   |-Identification    : %d\n",ntohs(iph->id));
	//fprintf(logfile,"   |-Reserved ZERO Field   : %d\n",(unsigned int)iphdr->ip_reserved_zero);
	//fprintf(logfile,"   |-Dont Fragment Field   : %d\n",(unsigned int)iphdr->ip_dont_fragment);
	//fprintf(logfile,"   |-More Fragment Field   : %d\n",(unsigned int)iphdr->ip_more_fragment);
	fprintf(logfile,"   |-TTL      : %d\n",(unsigned int)iph->ttl);
	fprintf(logfile,"   |-Protocol : %d\n",(unsigned int)iph->protocol);
	fprintf(logfile,"   |-Checksum : %d\n",ntohs(iph->check));
	fprintf(logfile,"   |-Source IP        : %s\n",inet_ntoa(source.sin_addr));
	fprintf(logfile,"   |-Destination IP   : %s\n",inet_ntoa(dest.sin_addr));
}

void print_tcp_packet(unsigned char* Buffer, int Size)
{
	unsigned short iphdrlen;

	struct iphdr *iph = (struct iphdr *)Buffer;
	iphdrlen = iph->ihl*4;

	struct tcphdr *tcph=(struct tcphdr*)(Buffer + iphdrlen);

	fprintf(logfile,"\n\n***********************TCP Packet*************************\n");	

	print_ip_header(Buffer,Size);

	fprintf(logfile,"\n");
	fprintf(logfile,"TCP Header\n");
	fprintf(logfile,"   |-Source Port      : %u\n",ntohs(tcph->source));
	fprintf(logfile,"   |-Destination Port : %u\n",ntohs(tcph->dest));
	fprintf(logfile,"   |-Sequence Number    : %u\n",ntohl(tcph->seq));
	fprintf(logfile,"   |-Acknowledge Number : %u\n",ntohl(tcph->ack_seq));
	fprintf(logfile,"   |-Header Length      : %d DWORDS or %d BYTES\n" ,(unsigned int)tcph->doff,(unsigned int)tcph->doff*4);
	//fprintf(logfile,"   |-CWR Flag : %d\n",(unsigned int)tcph->cwr);
	//fprintf(logfile,"   |-ECN Flag : %d\n",(unsigned int)tcph->ece);
	fprintf(logfile,"   |-Urgent Flag          : %d\n",(unsigned int)tcph->urg);
	fprintf(logfile,"   |-Acknowledgement Flag : %d\n",(unsigned int)tcph->ack);
	fprintf(logfile,"   |-Push Flag            : %d\n",(unsigned int)tcph->psh);
	fprintf(logfile,"   |-Reset Flag           : %d\n",(unsigned int)tcph->rst);
	fprintf(logfile,"   |-Synchronise Flag     : %d\n",(unsigned int)tcph->syn);
	fprintf(logfile,"   |-Finish Flag          : %d\n",(unsigned int)tcph->fin);
	fprintf(logfile,"   |-Window         : %d\n",ntohs(tcph->window));
	fprintf(logfile,"   |-Checksum       : %d\n",ntohs(tcph->check));
	fprintf(logfile,"   |-Urgent Pointer : %d\n",tcph->urg_ptr);
	fprintf(logfile,"\n");
	fprintf(logfile,"                        DATA Dump                         ");
	fprintf(logfile,"\n");

	fprintf(logfile,"IP Header\n");
	PrintData(Buffer,iphdrlen);

	fprintf(logfile,"TCP Header\n");
	PrintData(Buffer+iphdrlen,tcph->doff*4);

	fprintf(logfile,"Data Payload\n");
	PrintData(Buffer + iphdrlen + tcph->doff*4 , (Size - tcph->doff*4-iph->ihl*4) );

	fprintf(logfile,"\n###########################################################");
}

void print_udp_packet(unsigned char *Buffer , int Size)
{

	unsigned short iphdrlen;

	struct iphdr *iph = (struct iphdr *)Buffer;
	iphdrlen = iph->ihl*4;

	struct udphdr *udph = (struct udphdr*)(Buffer + iphdrlen);

	fprintf(logfile,"\n\n***********************UDP Packet*************************\n");

	print_ip_header(Buffer,Size);			

	fprintf(logfile,"\nUDP Header\n");
	fprintf(logfile,"   |-Source Port      : %d\n" , ntohs(udph->source));
	fprintf(logfile,"   |-Destination Port : %d\n" , ntohs(udph->dest));
	fprintf(logfile,"   |-UDP Length       : %d\n" , ntohs(udph->len));
	fprintf(logfile,"   |-UDP Checksum     : %d\n" , ntohs(udph->check));

	fprintf(logfile,"\n");
	fprintf(logfile,"IP Header\n");
	PrintData(Buffer , iphdrlen);

	fprintf(logfile,"UDP Header\n");
	PrintData(Buffer+iphdrlen , sizeof udph);

	fprintf(logfile,"Data Payload\n");
	PrintData(Buffer + iphdrlen + sizeof udph ,( Size - sizeof udph - iph->ihl * 4 ));

	fprintf(logfile,"\n###########################################################");
}

void print_icmp_packet(unsigned char* Buffer , int Size)
{
	unsigned short iphdrlen;

	struct iphdr *iph = (struct iphdr *)Buffer;
	iphdrlen = iph->ihl*4;

	struct icmphdr *icmph = (struct icmphdr *)(Buffer + iphdrlen);

	fprintf(logfile,"\n\n***********************ICMP Packet*************************\n");	

	print_ip_header(Buffer , Size);

	fprintf(logfile,"\n");

	fprintf(logfile,"ICMP Header\n");
	fprintf(logfile,"   |-Type : %d",(unsigned int)(icmph->type));

	if((unsigned int)(icmph->type) == 11)
		fprintf(logfile,"  (TTL Expired)\n");
	else if((unsigned int)(icmph->type) == ICMP_ECHOREPLY)
		fprintf(logfile,"  (ICMP Echo Reply)\n");
	fprintf(logfile,"   |-Code : %d\n",(unsigned int)(icmph->code));
	fprintf(logfile,"   |-Checksum : %d\n",ntohs(icmph->checksum));
	//fprintf(logfile,"   |-ID       : %d\n",ntohs(icmph->id));
	//fprintf(logfile,"   |-Sequence : %d\n",ntohs(icmph->sequence));
	fprintf(logfile,"\n");

	fprintf(logfile,"IP Header\n");
	PrintData(Buffer,iphdrlen);

	fprintf(logfile,"UDP Header\n");
	PrintData(Buffer + iphdrlen , sizeof icmph);

	fprintf(logfile,"Data Payload\n");
	PrintData(Buffer + iphdrlen + sizeof icmph , (Size - sizeof icmph - iph->ihl * 4));

	fprintf(logfile,"\n###########################################################");
}

void PrintData (unsigned char* data , int Size)
{

	for(i=0 ; i < Size ; i++)
	{
		if( i!=0 && i%16==0)   //if one line of hex printing is complete...
		{
			fprintf(logfile,"         ");
			for(j=i-16 ; j<i ; j++)
			{
				if(data[j]>=32 && data[j]<=128)
					fprintf(logfile,"%c",(unsigned char)data[j]); //if its a number or alphabet

				else fprintf(logfile,"."); //otherwise print a dot
			}
			fprintf(logfile,"\n");
		} 

		if(i%16==0) fprintf(logfile,"   ");
			fprintf(logfile," %02X",(unsigned int)data[i]);

		if( i==Size-1)  //print the last spaces
		{
			for(j=0;j<15-i%16;j++) fprintf(logfile,"   "); //extra spaces

			fprintf(logfile,"         ");

			for(j=i-i%16 ; j<=i ; j++)
			{
				if(data[j]>=32 && data[j]<=128) fprintf(logfile,"%c",(unsigned char)data[j]);
				else fprintf(logfile,".");
			}
			fprintf(logfile,"\n");
		}
	}
}

Compile : gcc sniffer.c

The program must be run as root user or superuser privileges. e.g. sudo ./a.out in ubuntu
The program creates raw sockets which require root access.

The output in the log file is something like this :


***********************TCP Packet*************************

IP Header
   |-IP Version        : 4
   |-IP Header Length  : 5 DWORDS or 20 Bytes
   |-Type Of Service   : 32
   |-IP Total Length   : 137  Bytes(Size of Packet)
   |-Identification    : 35640
   |-TTL      : 51
   |-Protocol : 6
   |-Checksum : 54397
   |-Source IP        : 174.143.119.91
   |-Destination IP   : 192.168.1.6

TCP Header
   |-Source Port      : 6667
   |-Destination Port : 38265
   |-Sequence Number    : 1237278529
   |-Acknowledge Number : 65363511
   |-Header Length      : 5 DWORDS or 20 BYTES
   |-Urgent Flag          : 0
   |-Acknowledgement Flag : 1
   |-Push Flag            : 1
   |-Reset Flag           : 0
   |-Synchronise Flag     : 0
   |-Finish Flag          : 0
   |-Window         : 9648
   |-Checksum       : 46727
   |-Urgent Pointer : 0

                        DATA Dump
IP Header
    45 20 00 89 8B 38 40 00 33 06 D4 7D AE 8F 77 5B         E ...8@.3..}..w[
    C0 A8 01 06                                             ....
TCP Header
    1A 0B 95 79 49 BF 5F 41 03 E5 5E 37 50 18 25 B0         ...yI._A..^7P.%.
    B6 87 00 00                                             ....
Data Payload
    3A 6B 61 74 65 60 21 7E 6B 61 74 65 40 75 6E 61         :kate`!~kate@una
    66 66 69 6C 69 61 74 65 64 2F 6B 61 74 65 2F 78         ffiliated/kate/x
    2D 30 30 30 30 30 30 31 20 50 52 49 56 4D 53 47         -0000001 PRIVMSG
    20 23 23 63 20 3A 69 20 6E 65 65 64 20 65 78 61          ##c :i need exa
    63 74 6C 79 20 74 68 65 20 72 69 67 68 74 20 6E         ctly the right n
    75 6D 62 65 72 20 6F 66 20 73 6F 63 6B 73 21 0D         umber of socks!.
    0A                                                      .

###########################################################

***********************TCP Packet*************************

IP Header
   |-IP Version        : 4
   |-IP Header Length  : 5 DWORDS or 20 Bytes
   |-Type Of Service   : 32
   |-IP Total Length   : 186  Bytes(Size of Packet)
   |-Identification    : 56556
   |-TTL      : 48
   |-Protocol : 6
   |-Checksum : 22899
   |-Source IP        : 74.125.71.147
   |-Destination IP   : 192.168.1.6

TCP Header
   |-Source Port      : 80
   |-Destination Port : 49374
   |-Sequence Number    : 3136045905
   |-Acknowledge Number : 2488580377
   |-Header Length      : 5 DWORDS or 20 BYTES
   |-Urgent Flag          : 0
   |-Acknowledgement Flag : 1
   |-Push Flag            : 1
   |-Reset Flag           : 0
   |-Synchronise Flag     : 0
   |-Finish Flag          : 0
   |-Window         : 44765
   |-Checksum       : 15078
   |-Urgent Pointer : 0

                        DATA Dump
IP Header
    45 20 00 BA DC EC 00 00 30 06 59 73 4A 7D 47 93         E ......0.YsJ}G.
    C0 A8 01 06                                             ....
TCP Header
    00 50 C0 DE BA EC 43 51 94 54 B9 19 50 18 AE DD         .P....CQ.T..P...
    3A E6 00 00                                             :...
Data Payload
    48 54 54 50 2F 31 2E 31 20 33 30 34 20 4E 6F 74         HTTP/1.1 304 Not
    20 4D 6F 64 69 66 69 65 64 0D 0A 58 2D 43 6F 6E          Modified..X-Con
    74 65 6E 74 2D 54 79 70 65 2D 4F 70 74 69 6F 6E         tent-Type-Option
    73 3A 20 6E 6F 73 6E 69 66 66 0D 0A 44 61 74 65         s: nosniff..Date
    3A 20 54 68 75 2C 20 30 31 20 44 65 63 20 32 30         : Thu, 01 Dec 20
    31 31 20 31 33 3A 31 36 3A 34 30 20 47 4D 54 0D         11 13:16:40 GMT.
    0A 53 65 72 76 65 72 3A 20 73 66 66 65 0D 0A 58         .Server: sffe..X
    2D 58 53 53 2D 50 72 6F 74 65 63 74 69 6F 6E 3A         -XSS-Protection:
    20 31 3B 20 6D 6F 64 65 3D 62 6C 6F 63 6B 0D 0A          1; mode=block..
    0D 0A                                                   ..

###########################################################

Note

1. The above sniffer picks up only TCP packets, because of the declaration :

sock_raw = socket(AF_INET , SOCK_RAW , IPPROTO_TCP);

For UDP and ICMP the declaration has to be :

sock_raw = socket(AF_INET , SOCK_RAW , IPPROTO_UDP);
sock_raw = socket(AF_INET , SOCK_RAW , IPPROTO_ICMP);

You might be tempted to think of doing :
sock_raw = socket(AF_INET , SOCK_RAW , IPPROTO_IP);

but this will not work , since IPPROTO_IP is a dummy protocol not a real one.

2. This sniffer picks up only incoming packets.

3. It provides the application with IP frames, which means that ethernet headers are not available.

4. It is not very accurate since it misses out some packets even in the incoming ones.

5. To write a proper sniffer use the libpcap. Code example here.

In Part 2 we shall see how the above mentioned drawbacks can be overcome.

Popularity: 65% [?]

Tags: linux, Sockets

About the Author: Binary Tides

28 Comments + Add Comment

Harish February 5, 2012 at 10:45 pm

Hi,

I tried to use the above program to get the ttl value from the ip header. Everything else compiles fine , but i get an error when i try to reference the ttl value

struct iphrd *ip_header = (struct iphrd *)buffer;

int recv_hopcount = (unsigned int)(ip_header->totlen);

Error: dereferencing pointer to an incomplete type

Any help.

Reply
- Harish February 5, 2012 at 10:46 pm
  
  Sorry make it
  struct iphrd *ip_header = (struct iphrd *)buffer;
  
  int recv_hopcount = (unsigned int)(ip_header->ttl);
  
  Reply
  - Binary Tides February 6, 2012 at 3:03 pm
    
    it should be struct iphdr*
    
    Reply
samualY January 22, 2012 at 10:12 am

How hard would it be to take the code you’ve provided above, rewrite it for ipv6 ?
I have been giving it a try, I feel I just don’t understand enough. The program above compiles and runs great !

Reply
- Binary Tides January 23, 2012 at 6:59 pm
  
  the above code does not process ipv6 packets. in ipv6 the processing has to be different since ip header structure is different.
  
  Reply
chirag November 30, 2011 at 8:01 pm

i got this error while i compile this code:

sachin@ubuntu:~$ sudo -s
root@ubuntu:~# cd Documents/
root@ubuntu:~/Documents# gcc -c sniffer.c
sniffer.c: In function ‘main’:
sniffer.c:63:46: warning: incompatible implicit declaration of built-in function ‘malloc’
sniffer.c:95:9: warning: passing argument 5 of ‘recvfrom’ from incompatible pointer type
/usr/include/sys/socket.h:166:16: note: expected ‘struct sockaddr * __restrict__’
but argument is of type ‘struct sockaddr_in *’
sniffer.c: In function ‘print_ip_header’:
sniffer.c:203:5: warning: incompatible implicit declaration of built-in function ‘memset’
sniffer.c: At top level:
sniffer.c:249:6: warning: conflicting types for ‘print_tcp_packet’
sniffer.c:159:13: note: previous implicit declaration of ‘print_tcp_packet’ was here
sniffer.c:343:6: warning: conflicting types for ‘print_udp_packet’
sniffer.c:169:13: note: previous implicit declaration of ‘print_udp_packet’ was here
sniffer.c:489:6: warning: conflicting types for ‘PrintData’
sniffer.c:321:5: note: previous implicit declaration of ‘PrintData’ was here

please help me…how i run this program.

Thanks
Chirag Verma

Reply
- Binary Tides November 30, 2011 at 8:33 pm
  
  the code should still compile and the a.out file would be created.
  
  Reply
sri November 19, 2011 at 9:05 am

sir this program is only tracing tcp packets .what is the proper output of this code.can u just send me the output details plzzzzzzz

Reply
- Binary Tides December 1, 2011 at 3:18 pm
  
  Yes, this will capture only TCP packet because of the socket definition as :
  sock_raw = socket(AF_INET , SOCK_RAW , IPPROTO_TCP);
  
  For UDP and ICMP you have to use :
  sock_raw = socket(AF_INET , SOCK_RAW , IPPROTO_UDP);
  sock_raw = socket(AF_INET , SOCK_RAW , IPPROTO_ICMP);
  
  It is also possible to capture all packets together using linux sockets. Check :
  
  http://www.binarytides.com/blog/packet-sniffer-code-in-c-using-linux-sockets-bsd-part-2/
  
  Libpcap can also be used :
  
  http://www.binarytides.com/blog/c-packet-sniffer-code-with-libpcap-and-linux-sockets-bsd/
  
  Reply
ant November 12, 2011 at 7:50 pm

Sry for dupled- add if it’s possible.

recvfrom seems can use non- connection-oriented sockets. It’s a wonder for me.
But, how to make it listen the port I need?

Reply
- Binary Tides December 1, 2011 at 3:21 pm
  
  you cannot make a raw socket listen to a port.
  The concept of port exists for TCP socket.
  
  Reply
ant November 12, 2011 at 7:23 pm

How can that work, if there’s no even bind?! Only creating socket- no binding and istening! No parameters added to RAW socket!
Or maybe it has some explanations?
When I ran that, I saw no output, only “Starting..” It loop into recvfrom and does nothing.

Reply
jess August 8, 2011 at 8:27 am

For sniffing packets from other host, you have to set protocol to ETH_P_ALL

Reply
nst July 9, 2011 at 12:02 pm

i am getting an error “libpcap.so.1 cannot open object file”, i am using RHEL and libpcap-1.1.1

Reply
Thamir July 4, 2011 at 9:53 am

suppose that I want to run this code under win7 platform what can I do ??

Reply
- Binary Tides December 1, 2011 at 3:42 pm
  
  For windows, winsock can be used. Check this :
  
  http://www.binarytides.com/blog/packet-sniffer-code-in-c-using-winsock/
  
  Also check winpcap.
  
  Reply
anjibabu June 29, 2011 at 11:40 am

Add fflush(logfile);
at the end of each print_xxxx_xxxx() method;
i.e
after fprintf(…) statements.
then one can able to see the log messages in log file.

Reply
SK March 24, 2011 at 10:00 pm

error: ‘struct tcphdr’ has no member named ‘th_flags’
how to solve this??

Reply
shriket January 26, 2011 at 6:23 am

hi,
the above program is gettin compiled with some warnings but at run time it gives the error like” error while loading shared libraries:libpcap.so.1:cannot open shared object file:no such file or directory”

Reply
mullai December 22, 2010 at 9:34 am

sir i want packet sniffer source code in c for (small programs)

Reply
sajid November 25, 2010 at 6:31 pm

please tell me the command sequence to sniff ip ipsec and pptp packet using linux and c++
Please Help

Reply
ksrpaniraj September 14, 2010 at 5:32 am

I still could not figure out how to capture icmp packets. Icmp packets doen’t get incremented. I actually wanted to capture vlan id. Can anyone have the solution for this

Reply
- Binary Tides December 1, 2011 at 6:37 pm
  
  to capture icmp packets create socket like this :
  
  sock_raw = socket(AF_INET , SOCK_RAW , IPPROTO_ICMP);
  
  Reply
faeze August 14, 2010 at 8:09 am

hi
i have the same problem. Does anyone solve it? or have another code for sniffing? Can anyone suggest me some reffrences for raw socket programming?

Reply
guddu July 20, 2010 at 10:16 am

@sumit

The above program will work if you edit the statement
sock_raw = socket(AF_INET , SOCK_RAW , IPPROTO_TCP); to
sock_raw = socket(AF_INET , SOCK_RAW , IPPROTO_UDP);

(atleast in my case it was working)
but there’s still a bug
it just filters out the UDP Packets.
also if anyone can help me with how to enable timestamp option in IP packets

Reply
Sumit July 14, 2010 at 9:58 am

hi
i have bee trying to run the above c program in my system but its not working. Though the compilation is done with some warnings but the execution gets stuck.Log file is created but its blank.
i want to know if i am doing it right way or some other steps are involved.
the program doesn’t ask any port address to sniff data from.

Please help
Thank you

Reply
bari May 28, 2009 at 12:40 pm

pleas have you a windows version of sniffer

badr-bari@hotmail.com

Reply
- Binary Tides December 1, 2011 at 6:39 pm
  
  its here :
  http://www.binarytides.com/blog/packet-sniffer-code-in-c-using-winsock/
  
  Reply