Won't work without a router

[jobattle]

I have been working on some socket related programming for a windows platform and I have found that my programs only work when I am connected to a router. I originally installed windows on a laptop (SP) so I could test a pair of UDP programs (attached) but I did not want to install security programs on the machine so I decided not to EVER connect it to the internet. However, I found that unless I connected the machine to at least a router, the programs would not work. I thought they would communicate over localhhost no matter what, but that does not appear to be true and I don't understand why.

When connected to the other machine, this is what the ipconfig and routing table looks like:

Ethernet adapter Local Area Connection:
Connection-specific DNS Suffix . :
Autoconfiguration IP Address. . . : 169.254.212.222
Subnet Mask . . . . . . . . . . . : 255.255.0.0
Default Gateway . . . . . . . . . :

=========================================
Interface List
0x1 ........................... MS TCP Loopback interface
0x2 ...00 11 43 cc aa 7f ...... Broadcom 570x Gigabit Integrated Controller - Packet Scheduler Miniport
==========================================
Active Routes:
Network Destination Netmask Gateway Interface Metric
127.0.0.0 255.0.0.0 127.0.0.1 127.0.0.1 1
169.254.0.0 255.255.0.0 169.254.212.222 169.254.212.222 20
169.254.212.222 255.255.255.255 127.0.0.1 127.0.0.1 20
169.254.255.255 255.255.255.255 169.254.212.222 169.254.212.222 20
224.0.0.0 240.0.0.0 169.254.212.222 169.254.212.222 20
255.255.255.255 255.255.255.255 169.254.212.222 169.254.212.222 1
=======================================
Persistent Routes:
None

When I unplug the connection, this is the results:

Ethernet adapter Local Area Connection:
Media State . . . . . . . . . . . : Media disconnected

================================================
Interface List
0x1 ........................... MS TCP Loopback interface
0x2 ...00 11 43 cc aa 7f ...... Broadcom 570x Gigabit Integrated Controller - Packet Scheduler Miniport
================================================
Active Routes:
Network Destination Netmask Gateway Interface Metric
127.0.0.0 255.0.0.0 127.0.0.1 127.0.0.1 1
255.255.255.255 255.255.255.255 255.255.255.255 2 1
================================================
Persistent Routes:
None

Here are the short test programs I wrote:

//------------------------------------------
// client.c
//------------------------------------------

#include <winsock.h>
#include <stdio.h>
#include <string.h>
#include <sys/time.h>
#include <stdlib.h>

#define REMOTE_SERVER_PORT 1500
#define MAX_MSG 1000
#define JMAX 24
#define IMAX 10

int main(int argc, char *argv[])
{
WSADATA wsadata;
int sd, rc;
struct sockaddr_in cliAddr, remoteServAddr;
struct hostent *h;
char teststring[MAX_MSG];
unsigned char i,j,k;
for(i=0;i<IMAX;i++)
{
for(j=0;j<JMAX;j++)
{
teststring[((25*i)+j)] = j + 65 ;
}
}
teststring[IMAX*JMAX]=0x00;
WSAStartup(MAKEWORD(2,2),&wsadata);
if(argc<2)
{
argv[1]="localhost";
}
printf("argv[1] = %s\n",argv[1]);

h = gethostbyname(argv[1]);

if(h==NULL)
{
printf("%s: unknown host '%s' \n", argv[0], argv[1]);
exit(1);
}

printf("%s: sending data to '%s' (IP : %s) \n", argv[0], h->h_name, inet_ntoa(*(struct in_addr *)h->h_addr_list[0]));

remoteServAddr.sin_family = h->h_addrtype;
memcpy((char *) &remoteServAddr.sin_addr.s_addr, h->h_addr_list[0], h->h_length);
remoteServAddr.sin_port = htons(REMOTE_SERVER_PORT);

sd=socket(AF_INET, SOCK_DGRAM, 0);
if(INVALID_SOCKET == sd)
{
perror("Could not create socket");
exit(1);
}

cliAddr.sin_family = AF_INET;
cliAddr.sin_addr.s_addr = htonl(INADDR_ANY);
cliAddr.sin_port = htons(0);

rc = bind(sd, (struct sockaddr *) &cliAddr, sizeof(cliAddr));
if(rc<0)
{
printf("%s: cannot bind port\n", argv[0]);
exit(1);
}

printf("%s\n",teststring);

for(i=0;i<255;i++)
{
rc = sendto(sd, teststring, 950, 0, (struct sockaddr *) &remoteServAddr, sizeof remoteServAddr);
if(rc<0)
{
printf("%s: cannot send data %d \n",argv[0],i-1);
close(sd);
exit(1);
}
}
closesocket(sd);
WSACleanup();
return 1;

}

//-------------------------------------------
// server.c
//-------------------------------------------

#include <winsock.h>
#include <stdio.h>
#include <string.h>
#include <sys/time.h>
#include <stdlib.h>

#define LOCAL_SERVER_PORT 1500
#define MAX_MSG 1000
#define RECORDSIZE 240

struct timeval tim;
double tStart, tStop, tDelta, tTotal, tThis, tPrev;
unsigned int i;

int main(int argc, char *argv[])
{
WSADATA wsadata;
int sd, rc, n, nBytes;
int cliLen;
struct sockaddr_in cliAddr, servAddr;
char msg[MAX_MSG];

LARGE_INTEGER lPreTime, lPostTime, lFrequency;
float lPassTick;
float lPassTime;

LARGE_INTEGER lStartTime, lStopTime;

WSAStartup(MAKEWORD(2,2), &wsadata);

sd=socket(AF_INET, SOCK_DGRAM, 0);
if(INVALID_SOCKET == sd)
{
perror("Could not create socket");
exit(1);
}

servAddr.sin_family = AF_INET; //bind local server port
servAddr.sin_addr.s_addr = htonl(INADDR_ANY);
servAddr.sin_port = htons(LOCAL_SERVER_PORT);
rc = bind (sd, (struct sockaddr *) &servAddr,sizeof(servAddr));
if(rc<0)
{
printf("%s: cannot bind port number %d \n", argv[0], LOCAL_SERVER_PORT);
exit(1);
}
i=0;
printf("Listening on Port %u for UDP packets\n", LOCAL_SERVER_PORT);
while(i<254)
{
memset(msg,0x0,MAX_MSG);
cliLen = sizeof(cliAddr);
n = recvfrom(sd, msg, MAX_MSG, 0, (struct sockaddr *) &cliAddr, &cliLen);
if(n<0)
{
printf("%s: cannot receive data \n",argv[0]);
continue;
}
i++;
if(i==2)
{
QueryPerformanceCounter(&lPreTime);
}
if(i==201)
{
QueryPerformanceCounter(&lPostTime);
}
}

if(i=201)
{
QueryPerformanceFrequency(&lFrequency);
lPassTick = (float)(lPostTime.QuadPart - lPreTime.QuadPart);
lPassTime = (float)lPassTick/(float)lFrequency.QuadPart;
nBytes = RECORDSIZE*200;
printf("tTotal = %0.6lf ntotal = %d Data Rate = %0.2lf MB/s\n",lPassTime,nBytes,(float)nBytes/(lPassTime*1000000));
//return 0;
}
closesocket(sd);
QueryPerformanceCounter(&lStartTime);
//sleep(10000);
QueryPerformanceCounter(&lStopTime);
lPassTick = (float)(lStopTime.QuadPart - lStartTime.QuadPart);
lPassTime = (float)lPassTick/(float)lFrequency.QuadPart;
printf("ten sec = %0.6lf sec\n",lPassTime);
WSACleanup();
}

 

[PhilFrisbie]

There is nothing wrong with your code; it is another Windows "helpful feature" that MS added to XP. When XP does not detect a network not even the loopback addresses will work. The way to get around this issue is to install the loopback network adapter. Here are the full instructions form a Microsoft article:

1. Click Start, and then click Control Panel.
2. If you are in Classic view, click Switch to Category View under Control Panel in the left pane.
3. Double-click Printers and Other Hardware, and then click Next.
4. Under See Also in the left pane, click Add Hardware,and then click Next.
5. Click Yes, I have already connected the hardware, and then click Next.
6. At the bottom of the list, click Add a new hardware device, and then click Next.
7. Click Install the hardware that I manually select from a list, and then click Next.
8. Click Network adapters, and then click Next.
9. In the Manufacturer box, click Microsoft.
10. In the Network Adapter box, click Microsoft Loopback Adapter, and then click Next.
11. Click Finish.