Connecting to Server

I'm working on this client program in C, but it can never connect to the server. The Server is coded in C as well, but it is in UNIX, this is for my work. Basically they want me to code the client program in Windows so they can have a windows version running, however, I can never get it to get authorization from the server. The part where it rejects me is below

Code:

Code:

---


// server.c in UNIX

 /* The client makes a simple identification */
                if(fgets(line,MAXLINE,fdr) == NULL) goto finish;
                /*if(sscanf(line,"%s %s %s",who,passwd,version) != 3) goto finish;*/
                strcpy(interface, "stpc");
                if(sscanf(line, "%s %s %s %s",who,passwd,version,interface) < 3) goto finish;
                // this printf ensures that line has an interface
                // for the logs
                sprintf(line, "%s %s %s %s\n",who,passwd,version,interface);
                if(strcmp(passwd,PASSWD) != 0) goto finish;
                fprintf(stplog," %s %s %s",timestamp(),whoami,line);
                fflush(stplog); 
 
                /* Let the client know we are connected */
                fprintf(fdw,"CONNECTED\n"); 
                fflush(fdw); 


that was the server portion, and now below is the one I am trying to code, which is in windows.

---

Code:

Code:

---


// client.c in windows 

  fd_rd = _open_osfhandle(ws_sockfd, 0);

        if (fd_rd == -1) exit(-1);


            ws_fdr= fdopen(fd_rd,"r");
       
            ws_fdw= fdopen(fd_rd,"w");
               
 
         

          if( ws_fdr == NULL || ws_fdw == NULL)
            err(FATAL,"STP: cannot open ws_fdw/ws_fdr\n");
         
          /* send authorization */
       
      printf("Sending authorization!\n");
          sprintf(line,"%s %s %s %s\n","STP",PASSWD,VERSION,"stpc"); // sets line to the ip, password, version, and interface
       
          ws_putline(line);
          fflush(ws_fdw);
          printf("Authorization sent, awaiting confirmation!\n");
         
          /* get connection acknowledgement */

          /*

                Below is where we get our
                Connection failures


      */
          ws_getline(line,MAXLINE);
          if(strcmp(line,"CONNECTED\n") != 0) {
            err(WARN,"STP: Connection rejected by waveserver - %s\n", line);
            continue;
          }



int ws_getline(char *str, int maxlen)
  {
        char *p, *fgets();
        p= fgets(str,maxlen,ws_fdr);
        if(p == NULL) return(EOF);
        return(strlen(p));
  }


void ws_putline(char *str)
  {
        fwrite(str,1,strlen(str),ws_fdw);
        fflush(ws_fdw);
  }

---

Basically it's trying to send the server the info, which are the password, version, interface and STP. and then the server should verify it and then say OK, and copy "CONNECTED\n" into line, and the we should be connected. On UNIX, both the client program and Server work fine. Please help, thanks.

Code:

---

  fd_rd = _open_osfhandle(ws_sockfd, _O_RDONLY);

        if (fd_rd == -1) exit(-1);


            ws_fdr= fdopen(fd_rd,"r");
       
            ws_fdw= fdopen(fd_rd,"w");

---

What is wrong here? You are trying to open the read-only fd returned by _open_osfhandle() to write on.
Try:

Code:

---

  fd_rd = _open_osfhandle(ws_sockfd, _O_RDWR);

---

You need to include <fcntl.h> for these constants.

Also, your code is a buffer overrun waiting to happen:

Code:

---

                if(sscanf(line, "%s %s %s %s",who,passwd,version,interface) < 3) goto finish;
                // this printf ensures that line has an interface
                // for the logs
                sprintf(line, "%s %s %s %s\n",who,passwd,version,interface);

---

If you need further help, could you outline what your program is doing currently? What does the server receive? Where exactly does the client stop? How does it stop, is it waiting for a reply from the server?

Thanks, i changed what you said to change. I was instructed not to change the server file, this is for my work, im interning at this place, and they want me to make it run on windows. But as far as what the server is getting, the first parameter is who the user is i think, and its just STP, and then the password and version are sent in, password "stpisgreat" and version is "1.4" and then the interface, which is just a string "stpc". I dont know what the point to those are but thats the way they designed it. There a site where I can post both the client and server programs on so you can see the entire code, which so ill send you those right now. And thanks a lot for all the help, I really appreciate it, Ive been

Heres the client.c program:

http://sourcepost.sytes.net/sourcevi...ource_id=14705

And here's the server program:

http://sourcepost.sytes.net/sourcevi...ource_id=14706

On the client.c program, the lines in question are between
00630 to 00670

and for the server program: 00210 to 00230.

Thanks for all your help. I definitely need it. I hope you can help me solving this problem, Ive spent since last thursday trying to figure it out.

You need to tell me how it is failing. Can I assume it is failing here:

Code:

---

              ws_getline(line,MAXLINE);
              if(strcmp(line,"CONNECTED\n") != 0) {
                err(WARN,"STP: Connection rejected by waveserver - %s\n", line);
                continue;
              }

---

If so, what is the server returning? What is the contents of line at this point?

EDIT:
Also try changing to:

Code:

---

            ws_fdr= fdopen(fd_rd,"rb");
       
            ws_fdw= fdopen(fd_rd,"wb");

---

This will open the streams as binary and avoid the line ending issue between unix/windows, although I doubt this is the problem.

Oh ok, well I do believe that is where it is failing, for some reason, it is not equal to CONNECTED, however, on UNIX, that function works and the server connects. I checked on the debugger, line is equal to STP stpisgreat 1.4 stpc. I dont understand why it would work on UNIX but not on windows

Code:

---

              sprintf(line,"%s %s %s %s\n","STP",PASSWD,VERSION,"stpc");
              ws_putline(line);
              fflush(ws_fdw);
             
              /* get connection acknowledgement */
              ws_getline(line,MAXLINE);
              if(strcmp(line,"CONNECTED\n") != 0) {
                err(WARN,"STP: Connection rejected by waveserver - %s\n", line);
                continue;
              }

---

>> line is equal to "STP stpisgreat 1.4 stpc" <<
This is what you put into the line buffer with the call to sprintf(). So now we know that the ws_getline() call is failing (otherwise it would replace the contents of the line buffer). ws_getline() could be failing because ws_putline() is failing(ie. nothing has been sent to the server). You need to check the return value of fwrite() in ws_putline(). And did you try the binary mode I suggested in the previous post?

Yeah I just tried th binary right now, still didnt work. I'll work on this later tomorrow, I have work in the morning, i did try checking the ws_getline and ws_putline functions in the debugger, but line was still the same. Ill work on it tomorrow. thanks for all the help. ill get back to you tomorrow about this.

gnite

ok, i tried looking through the debugger. I noticed that when it would assign the values of the password, interface, and version, etc. it would have this other character in the end, so to test it out I used strcpy(line, "STP stpisgreat 1.4 stpc"), but I still got the same error. I also noticed that in the putline function, fwrite returns 19 characters, which is right, since the string is from 0-19. Here is where I think the error is occurring. In the ws_getline() function.

below is the code:

Code:

---


int ws_getline(char *str, int maxlen)
  {
        char *p, *fgets();
        p= fgets(str,maxlen,ws_fdr);
        if(p == NULL) return(EOF);
        return(strlen(p));
  }

---

if p returns NULL, then there was an error. And that is exactly what is happening. I just noticed this using the debugger. So there is an error occuring within this function, but i dont know why that is.

Also, one more thing. If you want to run my actual program, just copy and paste the client.c program, the server program is running on the net, so you can actually try to connect to it. I'm not suppose to change anything on the server.c program, they just let me take a look at it since I was having trouble with it.

Hope you can help me solve this problem. Thanks.

>> it would have this other character in the end <<
That is the new line character('\n').

Code:

---

        char *p, *fgets();

---

What is this? Remove the highlighted bit and tell me if it works.

Did that, it didnt work.

I count 23 characters in "STP stpisgreat 1.4 stpc\n", not 19!

Youre right, the reason why it was 19 for me, and now back to 23 is because in the code, you can take out the stpc part and just insert the first three items. The server will automatically put the stpc in if im not mistaken. But Ive put back the stpc in, and now its 23 again.

Code:

---

                        if(fgets(line,MAXLINE,fdr) == NULL) goto finish;

---

Is it possible to tell me what the server is receiving? That is, the contents of line.

I thought the server was receiving in the ws_putline function. Here's how it looks

Code:

---

void ws_putline(char *str)
  {
        fwrite(str,1,strlen(str),ws_fdw);
        fflush(ws_fdw);
  }

---

and we do call the ws_putline function, and then afterwards the getline function.

But is the server actually receiving what we have sent?

Code:

---

                    fprintf(stplog," %s %s %s",timestamp(),whoami,line);

---

You should be able to look in the stplog to see if you are getting to that point.

I think timestamp is the time the user logs on.

in the server code, here's how timestamp() is defined. its actually a structure.

Code:

---


char *  timestamp() 
  { 
        char *ctime(); 
        static char buf[32];
        time_t t, time();
        t= time( (time_t *)(0));
        strcpy(buf,ctime(&t)); 
        buf[24]= '\0'; /* get rid of newline */
        return(buf);
  }

---

whoami is is basically the address coming in. we initialize it by doing this:

Code:

---

/* Process one connection */
                len = sizeof(cliaddr);
                if( (connfd = accept(listenfd, (SA *) &cliaddr, &len)) < 0)
                  { 
                        if(errno == EINTR) continue;
                        exit(-1);
                  } 
                  // WHOAMI INITIALIZED BELOW
                strcpy(whoami, inet_ntop(AF_INET,&cliaddr.sin_addr,buff,sizeof(buff)));

---

and line is what is equal to the stuff coming in, like the interface, password, version, etc.

so it writes all of that to stplog.

the thing is, the server is being run on UNIX, so i dont know howd id do that, unless Id have to go back and make a copy of the server.c program, convert that to make it run on windows and then see what happens. I dont know how else i could get access to stplog.

It looks like fgets doesn't work in this situation. I'm looking at it.

I just noticed that on the putline function, it gets written, but when it does fflush, its returning -1.

here's the function:

Code:

---


void ws_putline(char *str)
  {
        fwrite(str,1,strlen(str),ws_fdw); // writes 23 characters
        fflush(ws_fdw); // returns -1
  }

---

Yes, I've replicated your error. I don't think writing through the stream functions is going to work. I think you'll have to get rid of of the _open_osfhandle() and fdopen() calls and use the raw socket functions. I'm sorry for wasting your time.

Here is the new version of ws_putline():

Code:

---

void ws_putline(char *str)
  {
        if (send(ws_sockfd, str, strlen(str), 0) == SOCKET_ERROR)
        {
                printf("send() failed with error %d\n", WSAGetLastError());
        }
  }

---

Similarly ws_putdata() becomes:

Code:

---

int ws_putdata(int *buf, int ndata)
  {
            int n = send(ws_sockfd, buf, ndata, 0);

            if (n == SOCKET_ERROR)
            {
                printf("send() failed with error %d\n", WSAGetLastError());
            }
            return(n);
    }

---

You didnt waste my time, dont worry about it. How do I used raw socket functions. I put in the new putline, it still didnt work, ill use the debugger to check out whats going wrong. I just dont know what raw sockets functions are.

ws_getdata() becomes:

Code:

---

        ws_getdata(int *buf, int ndata)
            {
            int n = recv(ws_sockfd, buf, ndata, 0);

            if (n == SOCKET_ERROR)
            {
                printf("recv() failed with error %d\n", WSAGetLastError());
            }
            return(n);
            }

---

for getline here's what i wrote, but i still got the same thing.

Code:

---


int ws_getline(char *str, int maxlen)
  {
        char *p;
//        p= fgets(str,maxlen,ws_fdr);
//        if(p == NULL) return(EOF);
//        return(strlen(p));

        int ret;

        ret = recv(ws_sockfd,p,maxlen,0);
        str=p;
        return ret;
  }

---

return is still -1.

for ws_putline(), i did pretty much what you said, I changed it a little.

Code:

---


void ws_putline(char *str)
  {
        //fwrite(str,1,strlen(str),ws_fdw); // writes 23 characters
        //fflush(ws_fdw);// returns EOF error. returns -1 value

        int n=0;
        if (send(ws_sockfd, str, strlen(str), 0) == SOCKET_ERROR)
        {
                printf("send() failed with error %d\n", WSAGetLastError());
        }
        else
        {
        n=        send(ws_sockfd, str, strlen(str), 0);
        n;
        str;

        }


  }

---

n is equal to 23 when this is said and done with

Here is an implementation of ws_getline():

Code:

---

int ws_getline(char *str, int maxlen)
{
        int total = 0;

        while (total < maxlen - 1)
        {
                /* Get a character */
                int ret = recv(ws_sockfd, str, 1, 0);

                if (ret == SOCKET_ERROR)
                {
                        printf("recv() failed with error %d\n", WSAGetLastError());
                        break;
                }
                else if (ret > 0)
                {
                        /* Increment received character count */
                        total++;
                        /* Check if we are finished this line */
                        if (*str == '\n') break;
                        /* Move to next character in buffer */
                        str++;
                }
        }

        *str = '\0';

        return total;
}

---

No, your ws_putline is calling send() twice. If you need the return value from send() use:

Code:

---

void ws_putline(char *str)
  {
        int n = send(ws_sockfd, str, strlen(str), 0);

        if (n == SOCKET_ERROR)
        {
                printf("send() failed with error %d\n", WSAGetLastError());
        }
  }

---

Once you have replaced the functions it should work. You can delete these lines entirely:

Code:

---

              fd_rd = _open_osfhandle(ws_sockfd, _O_RDWR);
       
                if (fd_rd == -1) exit(-1);
       
                ws_fdr= fdopen(fd_rd,"r"); 
           
                ws_fdw= fdopen(fd_rd,"w");
00640:         
           
           
       
              if( ws_fdr == NULL || ws_fdw == NULL)
                err(FATAL,"STP: cannot open ws_fdw/ws_fdr\n");

---

I tried that, it made my program freeze at the line

int ret = recv(ws_sockfd, str, 1, 0);

That means it is waiting to receive something. Could you post the new code?

I will, but should it take this long to receive, i mean its been sitting here for a while

I was also thinking, you know how I do have the ws_fdr and ws_fdw in the server, but i wont be using it in this, is that going to affect how this thing logs on or gets the password, version, interface, etc.?

What you do in the client will not change the server. You are still writing on the socket, whether you do it through ws_fdw or through ws_sockfd.

Is it working?

Quote:

---

Originally Posted by osal

I will, but should it take this long to receive, i mean its been sitting here for a while

---

__ No! __

Here's where i posted my code.

http://sourcepost.sytes.net/sourcevi...ource_id=14723

It's almost time for my lunch, I'm going to leave in about 20, and ill be back in an hour. so around 12:40 my time ill be going for lunch, i hope youll still be available by the time i come back.

The client.c program has been sitting here forever, and it hasnt gotten anything back. could it be possible that the program is frozen?

>> It's almost time for my lunch, I'm going to leave in about 20, and ill be back in an hour. so around 12:40 my time ill be going for lunch, i hope youll still be available by the time i come back. <<

No, I'll be gone, but I'll have alook at the new source code first.

>> The client.c program has been sitting here forever, and it hasnt gotten anything back. could it be possible that the program is frozen? <<

Well, it's waiting to receive data which is not coming, so you could call it frozen!

1. You missed my post on why your ws_putline() is wrong.

2.

Code:

---

00650:        printf("Sending authorization!\n");
              //sprintf(line, "%s %s %s %s\n","STP",PASSWD,VERSION,"stpc"); // sets line to the ip, password, version, and interface
              strcpy(line, "STP stpisgreat 1.4 stpc\n");
              ws_putline(line);

---

You are not finishing the string with a new line here. Add the highlighted portion. The server is probably waiting for a new line character in the call to fgets() and so is not sending a reply.

Let me know how you get on.

OK, i put that in, now it just does the same thing as it was before, its just not connecting.

Actually its almost being connected, whats getting copied to line is just Connected instead of CONNECTED\n

Yep, I just realised that my ws_getline() is removing the new line character. Here is a corrected version.

Code:

---

int ws_getline(char *str, int maxlen)
{
        int total = 0;

        while (total < maxlen - 1)
        {
                /* Get a character */
                int ret = recv(ws_sockfd, str, 1, 0);

                if (ret == SOCKET_ERROR)
                {
                        printf("recv() failed with error %d\n", WSAGetLastError());
                        break;
                }
                else if (ret > 0)
                {
                        /* Increment received character count */
                        total++;
                        /* Check if we are finished this line */
                        if (*str++ == '\n') break;
                }
        }

        *str = '\0';

        return total;
}

---

It should finally work!

Cool, it connects, now I gotta figure out how to fix the new error with. After it connects successfully, i get an error that states this :

"error message: unknown byte order on client"

So im going to try to figure out why its doing that. But thank you very much for all of your help! Would it be too much to ask if i could ask you more questions on my code?

thanks

Other improvements to note (sorry if these have been covered before):

- Prototype your functions properly
It's no good prototyping a function unless you're going to state what parameters it takes. So, this type of thing:
>void open_waveserver();
>void close_waveserver();
>int ws_getline();
is no good, use
>void open_waveserver(char *);
>void close_waveserver(void);
>int ws_getline(char *, int);
and fix all the others.
Also, all the #include statements should come before the prototypes.

- Function err().
This function needs a variable number of arguments. Here's a sample of a more suitable implementation:

Code:

---

void err(int mode, char *fmt, ...)
 {
  va_list arglist;
  va_start(arglist, fmt);
 
  printf ("Mode: %d : WSAGetLastError: %d\n", mode, WSAGetLastError());
  vfprintf(stderr, fmt, arglist);
  va_end(arglist);
 
  if (mode == FATAL)
  {
        exit(-1);
  }
 }

---

The same kind of thing goes for the report() function.

Sorry, the ws_getline I posted is still not quite right. Here is the corrected version:

Code:

---

int ws_getline(char *str, int maxlen)
{
        int total = 0;

        while (total < maxlen - 1)
        {
                /* Get a character */
                int ret = recv(ws_sockfd, str, 1, 0);

                if (ret == SOCKET_ERROR)
                {
                        printf("recv() failed with error %d\n", WSAGetLastError());
                        break;
                }
                else if (ret > 0)
                {
                        /* Increment received character count */
                        total++;
                        /* Check if we are finished this line */
                        if (*str++ == '\n') break;
                }
                else
                {
                        break;
                }
        }

        *str = '\0';

        return total;
}

---

Quote:

---

After it connects successfully, i get an error that states this :

"error message: unknown byte order on client"

---

Can you confirm that you have corrected the ws_putline() function? If not , it would be causing that error. Could you also post the new code(preferably with the corrections suggested by Hammer)?

Well, i just added the

Code:

---

else
{
  break;

}

---

now it goes it just keeps outputing the error over and over. The problem is within the receive() function in my program. I dont know how to fix it, it is between lines of 00400 and 00520.

here's the site where my code is located at.

http://sourcepost.sytes.net/sourcevi...ource_id=14735

Thanks for all your help.

One more thing. The error i do get states this:

"Error message: unknown byte order format"

and in the code before it hits the receive function, we do this so the server can establish teh byte order.

Code:

---

/* send a binary sample so the server can establish byte order */

               
          two= 2;
          ws_putdata(&two,4);
          fflush(ws_fdw);
          printf("We have now set up the byte order!\n");

---

Your ws_putline() is wrong! This is the third or fourth time I have pointed that out! Because you are sending the data twice in ws_putline() the server is not reading the two when it should. Here is a correct implementation of ws_putline():

Code:

---

void ws_putline(char *str)
  {
        int n = send(ws_sockfd, str, strlen(str), 0);

        if (n == SOCKET_ERROR)
        {
                printf("send() failed with error %d\n", WSAGetLastError());
        }
  }

---

That should get rid of the "unknown byte order format" error.

Then, go to line 55 and delete this line:

Code:

---

        FILE *ws_fdr, *ws_fdw;  // file read-in and write-out

---

We can't not use these successfully. So you will get warnings where you are trying to use them. Also delete this line:

Code:

---

        int fd_rd;

---

I have two ws_putlines..i have that one, and then putline2

the error is happening when it is trying to send the byte ordering to the server. i just emailed one of my co-workers she said since the server is in unix, the windows one either doesnt have it, or is different from the one on unix. i dont know how to convert the byte ordering the way its suppose to be.

this is what my co-worker said:
Interesting...

So there are two kinds of byte orders that I know of "little endian" and
"big endian". The difference is in how they order their bytes. For
example, 2 could be 00000010 or 01000000. The stp server tries to check
which order your using so that if it's not the same, it can swap the bytes
for you where necessary. Here's a code snippet from the server:

Code:

---

                /* Receive the sample '2', to get the byte-order of the
client */
                two= 0;
                fread(&two,1,4,fdr);
                if(two == 2)    byteswap= 0;  /* same order */
                else
                  {
                        if(two == 0x02000000 ) byteswap =1; /*reverse
order */
                        else
                          {
  if(two == 0x02000000 ) byteswap =1; /*reverse
order */
                        else
                          {
                                puterror("unknown byte-order on client -
cannot function - exit\n");
                                exit(-1);
                          }
                  }

---

So either windows has neither of those byte orders, or perhaps you are
neglecting to send the number 2 through to the server.

The unix client does this here:

Code:

---

        /* send a binary sample so the server can establish byte order */
          two= 2;
          ws_putdata(&two,4);
          fflush(ws_fdw);

---

sorry, u were right, it worked, thanks a lot!

[edit]
Posted while you were posting. :)
[/edit]

Argh!

>> I have two ws_putlines..i have that one, and then putline2<<

There is no putline2 in the code you posted. Either way you are using ws_putline():

Code:

---

          strcpy(line, "STP stpisgreat 1.4 stpc\n");
              ws_putline(line);

---

and it is wrong!

>> So either windows has neither of those byte orders, or perhaps you are
neglecting to send the number 2 through to the server. <<
No what is happening, which I've been pointing out repeatedly, is that you send the authorization line twice because of your version of ws_putline(). This means, that when the server comes to read the two, it is getting instead the second copy of the authorization line.

If you replace your ws_putline and delete the declaration line it will make things a lot easier.

Yeah, i did that, you were right, i had two ws_putdata(), and i changed the code, and it worked. I have a question, I mean everything works, but why did I have to use raw socket functions instead of doing it the way unix did it?

i changed the code of the ws_putline that is, not the putdata

Are you sure it is working? In the code you posted you are still using fread() at about 455 and ws_getline2() at about 495. Both of these are likely to fail.

>> I mean everything works, but why did I have to use raw socket functions instead of doing it the way unix did it? <<

In unix a socket handle is a normal file descriptor which you can pass to fdopen(). In windows a socket is not a C file descriptor and you can not pass it to fdopen. You are meant to be able to pass the socket to _open_osfhandle() to get a C file descriptor but it doesn't seem to work.

yeah its working, u can try it if you want, i posted it up, everything is working great, im not using ws_getline2() anymore. i took it out

That's great!

Thanks a lot, I owe you one...or maybe 10, or 100. I dont know, but thanks a lot, i didnt really know much about networking, they just had me doing this for my internship, so im learning as we speak. So thanks a lot, im going to try to read through the code to try to understand it better. Would it be a problem if i were to ask you a question about some of the stuff we went over some other time in a message or something?

Many people suggest Beej as a good guide to network programming. Unfortunately, some of it is unix specific but it is worth a read.

>> Would it be a problem if i were to ask you a question about some of the stuff we went over some other time in a message or something? <<
No problems.

Thanks a lot. :-)

>>unknown byte order format
Any reason you're not using ntohl() and htonl() etc?

Also, there's some good examples of read functions here:
http://cboard.cprogramming.com/showt...333#post321434
Adapt them to suit if you want.

thanks hammer