Thread: Raw Socket Client and Server Communication Problem

I have been trying to communicate between my client and server program. I have checked and rechecked the man pages and it seems my syntax is correct. I'm trying to send packets from my client to my server and the server prints out the host name. My server seemed to receive the packets once during testing. I say this because it printed out my "check statements" and seemed to find the host name from the sent packets. All it is doing now though is attempting to bind to the server's port and seems to be waiting on something to send from the client. If someone could take a look at this I would really appreciate it. Thank you for your time--rgpii.

Here is my code below:

ip and udp header file

Code:

//Header file for our ip header and udp header structures.
 
// The packet length
#define PCKT_LEN 8192
 
// Can create separate header file (.h) for all headers' structure
// The IP header's structure
struct ipheader {
 unsigned char      iph_ihl:4;// IP Header Length 
 unsigned char 	    iph_ver:4;//Internet Protocol
 unsigned char      iph_tos;//Type of Service
 unsigned short int iph_len;//Length of IP datagram. Must include UDP size.
 unsigned short int iph_ident;//ID sequence number.
 unsigned char      iph_flag;
 unsigned short int iph_offset;//Fragment offset-used for broken datagrams
 unsigned char      iph_ttl;//Time to live-amount of hops before packet is discarded.
 unsigned char      iph_protocol;//Transport layer protocol.UDP(17)
 unsigned short int iph_chksum;//Checksum total.Everytime header changes must be recalculated.
 unsigned int       iph_sourceip;//Source IP must be converted into binary. inet_pton()
 unsigned int       iph_destip;//Destination IP ""
};
 
// UDP header's structure
struct udpheader {
 unsigned short int udph_srcport;
 unsigned short int udph_destport;
 unsigned short int udph_len;
 unsigned short int udph_chksum;
};

Check Sum header file.

Code:

//Header file for the check sum algorithm.
unsigned short csum(unsigned short *buf, int nwords)

    {       //

            unsigned long sum;

            for(sum=0; nwords>0; nwords--)

                    sum += *buf++;

            sum = (sum >> 16) + (sum &0xffff);

            sum += (sum >> 16);

            return (unsigned short)(~sum);

    }

Client Program:

Code:

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/udp.h>
#include <string.h>
#include "ipudp.h"
#include "csum.h"

						/******Client Program*****/


int main(int argc, char *argv[])
{
printf("Beginning Raw Socket Programming\n");
//Variable Declarations 
int sfd;
char buffer[PCKT_LEN];
struct ipheader *ip=(struct ipheader*) buffer;//Rename to iph
struct udpheader *udp=(struct udpheader*)(buffer +sizeof(struct ipheader));//Rename to udph
struct sockaddr_in sin, din;//DOES NOT HAVE TO BE SIN AND DIN!!!
int one=1;
const int *val=&one;//Curious to the purpose of this? Test later with just constant integer.
memset(buffer,0,PCKT_LEN);//Memset to ensure no packet corruption?

//Baby Argument Checker
if(argc!=5){
printf("Invalid Parameters\n");
	}

/*Argument Checking*******This is the servers. The letters need to be changed back to the clients.
int argcounter;
printf("Number of arguments %d\n", argc);
for(argcounter=1;argcounter<14;argcounter++)
	{
	printf("Before switch argcounter is %d\n",argcounter);
	 switch(argv[argcounter][1])
		{
		case 'p':
		argcounter++;
		printf("Heck Yeah Made it to %s\n",argv[argcounter]);
		break;
		case 'r':		
		argcounter++;
		printf("Heck Yeah Made it to %s\n",argv[argcounter]);
		break;
		case 'q':
		argcounter++;
		printf("Heck Yeah Made it to %s\n",argv[argcounter]);
		break;
		case 'l':
		argcounter++;
		printf("Heck Yeah Made it to %s\n",argv[argcounter]);
		break;
		case 'f':
		argcounter++;
		printf("Heck Yeah Made it to %s\n",argv[argcounter]);
		break;
		case 'h':
		argcounter++;
		printf("Heck Yeah Made it to %s\n",argv[argcounter]);
		break;
		case 't':
		argcounter++;
		printf("Heck Yeah Made it to %s\n",argv[argcounter]);
		break; 
		default:
		printf("Incorrect Argument Use\n");
		break;
		}*/


//Creating a raw socket using the UDP protocol.
sfd=socket(PF_INET,SOCK_RAW,IPPROTO_UDP);
if(sfd<0){
perror("socket() error\n");
exit(-1);
}
else{
printf("Socket was created\n");
}
//The Address Familys for my sockadd_in structs.
sin.sin_family=AF_INET;
din.sin_family=AF_INET;
//Port Numbers--This will go in my argument checker.
sin.sin_port=htons(atoi(argv[2]));
din.sin_port=htons(atoi(argv[4]));
//IP Addresses--This will go in my argument checker--Used old way in internet example.(E.g "inet_address()")
if(inet_pton(AF_INET,argv[1],&sin.sin_addr)<0){
perror("inet_pton() error\n");
}
if(inet_pton(AF_INET,argv[3],&din.sin_addr)<0){
perror("inet_pton() error\n");
}
//Creating my own IP Header
ip->iph_ihl=4;
ip->iph_ver=4;
ip->iph_tos=16;
ip->iph_len=sizeof(struct ipheader)+sizeof(struct udpheader);
ip->iph_ident=htons(54321);
ip->iph_ttl=64;
ip->iph_protocol=17;
//Source IP Address
if(inet_pton(AF_INET,argv[1],&ip->iph_sourceip)<0){
perror("inet_pton() error\n");
}
if(inet_pton(AF_INET,argv[3],&ip->iph_destip)<0){
perror("inet_pton() error\n");
}
//Creating UDP Header
udp->udph_srcport=htons(atoi(argv[2]));
udp->udph_destport=htons(atoi(argv[4]));
udp->udph_len=htons(sizeof(struct udpheader));
//Calculating Checksum for my packet
ip->iph_chksum=csum((unsigned short*)buffer,sizeof(struct ipheader) + sizeof(struct udpheader));
//Informing the kernel not to fill the packet. We will do that.
if(setsockopt(sfd,IPPROTO_IP,IP_HDRINCL,val,sizeof(one))<0){
perror("setsockopt() error\n");
exit(-1);
}
else{
printf("setsockopt() is doing ok\n");
}

printf("Using:::::Source IP: %s port: %u, Target IP: %s port: %u.\n", argv[1], atoi(argv[2]), argv[3], atoi(argv[4]));
int count;
for(count = 0; count < 40; count++)
{
if(sendto(sfd,buffer,ip->iph_len,0,(struct sockaddr*)&sin,sizeof(sin))<0){
perror("sendto() error\n");
}
else{
printf("Count #%u - sendto() is OK\n", count);
sleep(2);
}
}
close(sfd);
return 0;
}

Server Program:

Code:

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/udp.h>
#include <string.h>
#include "ipudp.h"
#include "csum.h"
#define SERVER_PORT	5020 

	/******Server Program*****/*

int main(int argc, char* argv[])
{
//Variable Declarations
int sfd;
//int  new_sfd;
char buffer[PCKT_LEN];
char hbuf[NI_MAXHOST],sbuf[NI_MAXSERV];
//struct ipheader *ip=(struct ipheader*)buffer;//Rename to iph
//struct udpheader *udp=(struct udpheader*)(buffer + sizeof(struct ipheader));//Rename to udph
struct sockaddr_in sin, din;//DOES NOT HAVE TO BE SIN AND DIN!!!
//int one=1;
//**Unused Variable const int *val=&one;
struct sockaddr_storage inc_packet;
socklen_t inc_packetl;
int bytes_read;
memset(buffer,0,PCKT_LEN);
	
/*
//Argument Checking
int argcounter;
printf("Number of arguments %d\n", argc);
for(argcounter=1;argcounter<14;argcounter++)
	{
	printf("Before switch argcounter is %d\n",argcounter);
	 switch(argv[argcounter][1])
		{
		case 'p':
		argcounter++;
		printf("Heck Yeah Made it to %s\n",argv[argcounter]);
		break;
		case 'r':		
		argcounter++;
		printf("Heck Yeah Made it to %s\n",argv[argcounter]);
		break;
		case 'q':
		argcounter++;
		printf("Heck Yeah Made it to %s\n",argv[argcounter]);
		break;
		case 'l':
		argcounter++;
		printf("Heck Yeah Made it to %s\n",argv[argcounter]);
		break;
		case 'f':
		argcounter++;
		printf("Heck Yeah Made it to %s\n",argv[argcounter]);
		break;
		case 'h':
		argcounter++;
		printf("Heck Yeah Made it to %s\n",argv[argcounter]);
		break;
		case 't':
		argcounter++;
		printf("Heck Yeah Made it to %s\n",argv[argcounter]);
		break; 
		default:
		printf("Incorrect Argument Use\n");
		break;
		}
	}
*/
//Address Family
sin.sin_family=AF_INET;
din.sin_family=AF_INET;
//Port Numbers
sin.sin_port=htons(SERVER_PORT);
//din.sin_port=client port argument.
//IP Addresses
if(inet_pton(AF_INET,"127.0.0.1",&sin.sin_addr)<0){
perror("inet_pton() error\n");
}
else{
printf("inet_pton() doing ok\n");
}
//Include IP Address for Client

//Creating a raw socket using the UDP protocol.
sfd=socket(PF_INET,SOCK_RAW,IPPROTO_UDP);
if(sfd<0){
perror("socket() error\n");
exit(-1);
}
else{
printf("Socket was created\n");
}
//Binding our socket to our servers port.
if(bind(sfd,(struct sockaddr*)&sin,sizeof(sin))<0){
perror("bind() error\n");
exit(-1);
}
else{
printf("bind() is doing ok\n");
}
int x =0;
while(x!=10){
printf("Waiting after bind\n");
inc_packetl=sizeof(struct sockaddr_storage);
bytes_read=recvfrom(sfd,buffer,PCKT_LEN,0,(struct sockaddr*)&inc_packet,&inc_packetl);  
if(bytes_read==0){
printf("Message Read\n");
}
printf("Printing Buffer Stuff %s\n",buffer);
if(getnameinfo((struct sockaddr*)&inc_packet,inc_packetl,hbuf,sizeof(hbuf),sbuf,sizeof(sbuf),0)<0){
perror("getnameinfo() error\n");
}
else{
printf("Host name found\n");
}
printf("Host:%s,  Serv:%s\n",hbuf,sbuf); 
x++;
}
close(sfd);
return 0;
}

Ummmm... Why all the trouble to make your own headers when sockets builds it's own on the fly and attaches it to every datagram you send? Believe me it's using it's own headers not yours... all you're doing is making your code more complex than it needs to be...

Here's what I use...

Code:

// initialize Client port/return port number
WORD InitNetwork(WORD Port,HWND Win,PTCHAR Password)
  { WSADATA     wsadata;              // winsock startup
    TCHAR       hn[MAX_HOSTNAME];     // host name
    DWORD       hs = MAX_HOSTNAME;    // host name size
    SOCKADDR    la;                   // local address
    WORD        lp = Port;            // local port
    // Load the Winsock DLL
    if (WSAStartup(MAKEWORD(2,0),&wsadata))
      return 0;
    // initialize local socket
    hSocket = socket(AF_INET,SOCK_DGRAM,IPPROTO_UDP);
    if (hSocket == INVALID_SOCKET)
      return 0;
    // initialize localhost IP  
    GetComputerName(hn,&hs);
    if (!GetHostAddr(hn,Port,&la))
      return 0;
    // bind on user designated Port
    if(bind(hSocket,&la,sizeof(SOCKADDR)))
      return 0; 
     return lp; }

That sets up a listening UDP socket... from there just call sendto() and receivefrom()... there is absolutely no need to create your own headers, sockets does all that for you.

Originally Posted by Salem

It looks like copy/paste code from 3 different people.

Yep... scoop and poop .... Definately not the way to do things.

Sorry about the formatting. Is it against the rules if i repost the code again but formatted? It is necessary for me to create my own headers because that is part of my assignment. I also noticed the above poster is using "winsock"? I believe that is windows specific. Right? I am sorry I'm on a Linux machine. I am currently running Ubuntu. I don't know if that will help or not.