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06.22.2008 at 08:31AM PDT, ID: 23505779

	[x] Attachment Details

[C TCP server] Problem with Linked List, splitted string and while()

Asked by roccogalati in C Programming Language, CYGWIN, TCP/IP

Tags: C

Hi!

I will try to explain my problem as well as I can... i hope you can help me...
i tried so hard but i wasn't able to solve it...

i always have this file:

15 nick
25 marcus
18 sarah

and i add a function to my server which can send back to the client the age of each user, by giving it a text line.
Fo example, if client sends FIND10 where 1 and 0 are numbers on 16 bit in network byte order, the server has to send back the message HERE 1 15, where 1 is the text line where there is stored 15 which is the age of nick.
(0 specifies the end of command)

This works fine if the client ask for just a text line, but if he sends two consecutive FIND commands like: FIND1 and then FIND20 the server has a strange behavior.

It answer correctly for the first request, but then, for the second FIND command it doesn't send the correct value and i don't know the reason.

For each request the server has to answer like:
HERE text_line value(age)

so for a command like FIND30
it answers like:
HERE 3 18

i'm using a client to test it, and this is the result:

(./client_test) trace - send_bytes(FIND)
(./client_test) trace - send_netshort(1)
(./client_test) trace - send_netshort(0)
(./client_test) trace - expect_bytes:
- expected 'HERE'
- received 'HERE'
(./client_test) trace - expect_netshort: expected 1, received 1
(./client_test) trace - expect_netshort: expected 15, received 15
(./client_test) trace - send_bytes(FIND)
(./client_test) trace - send_netshort(2)
(./client_test) trace - send_netshort(0)
(./client_test) trace - expect_bytes:
- expected 'HERE'
- received 'HERE'
(./client_test) error - expect_netshort: expected 2, received 0
(./client_test) info - test 'FIND of age at the second line 2: 25' failed

client code for this is:

static struct {
char *cmd;
int id1, term;
char *status;
int val1;
char *msg;
}
cost_1[] = {
{ FIND, 1, 0, HERE, 2, "FIND of age at the first line 2: 25 1: 15" },
{ FIND, 2, 0, HERE, 25, "FIND of age at the second line 2: 25" },
{ FIND, 3, 0, HERE, 590, "FIND of age at the third line 2: 25: 18" },
};

for (i=0; i<sizeof(cost_1)/sizeof(cost_1[0]); i++) {
Send_bytes (sockfd, cost_1[i].cmd, sizeof(COST)-1);
Send_netshort (sockfd, cost_1[i].id1);
Send_netshort (sockfd, cost_1[i].term);
Expect_bytes (cost_1[i].msg, sockfd, cost_1[i].status, sizeof(HERE)-1);
      Expect_netshort (cost_1[i].msg, sockfd, cost_1[i].id1);
Expect_netshort (cost_1[i].msg, sockfd, cost_1[i].val1);
}

and it works fine. The problem is with my server.

In my server code I use this functiom to trap the command:

else if(strncmp(comando, "FIND", 4) == 0)
                   {
if (auth == 0)
                              {
Writeline(fd, noauth, strlen(noauth));
}
else {
if (llist->next == NULL )
                                     {
Writeline(fd, noob, strlen(noob));
}

else      if (llist ->next != NULL )
                                      {
char * temp = comando+4;
short arr;
int val = 0;

do
{
Writeline(fd, here, strlen(here));
       memcpy(&arr, temp, 2);
Writeline(fd, &arr, 2);
       temp = temp + 2;
val = ntohs(arr);
search_value(llist, val, fd);

} while (val);
}
}
                         }

and my search_value() function is:

int search_value(struct NODE *llist, int text_line, int fd) {
int retval = -1;
int i = 1;
int net;

while(llist != NULL) {
if(llist->line == text_line){ /* if there is a result for the request */
      net = htons(llist->code);
      Writeline(fd, &net, 2); /* send the value to the client */
      llist = llist->next;
return i;
      }

else i++;
llist = llist->next;

}
if (i != 1) /* else htons(0) si returned */
net = htons(65535); //if there is no object, i return HERE 65535
Writeline(fd, &net, 2);
return retval;
}

and i load the content of the text file with this:

void load_file_in_list(){

llist = (struct NODE *)malloc(sizeof(struct NODE));
llist->code = 0;
llist->next = NULL;
llist->size = 0;
llist->line = 0;

FILE * pFile;
char buffer [100];
int code;
char name[1000];

pFile = fopen (objs_file , "r");
if (pFile == NULL) perror ("Error opening file");
else
{
while ( fgets (buffer , 100 , pFile) != NULL )
{

       sscanf(buffer,"%d %s \n", &code, name);
       line++;
       append_node(llist, name, code, line); /* insert values in the list */
       size++;
       }
       fclose (pFile);
}

}

I hope someone can help me... i'd really want to solve this problem...
i'm posting the entire code below...

( it can be because i use a global variable (int line=0) in order to count lines in the text_file in my load_file_in_list()? )

p.s. if you need i can attach my server source file...

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             //search function()
 
int search_value(struct NODE *llist, int text_line, int fd) {
 int retval = -1;
 int i = 1;
 int net;
 
     
  while(llist != NULL) {
  if(llist->line == text_line){ /* if there is a result for the request */
	net = htons(llist->code);
	Writeline(fd, &net, 2);             /* send the value to the client */
	llist = llist->next;
    return i;
	}	
  
  else  i++;
  llist = llist->next;
 
 }
 if (i != 1)             /* else htons(0) si returned */
 net = htons(65535);
 Writeline(fd, &net, 2);
 return retval;
}
 
// end
 
 
 
// How i trap the command
while (comando) 
   {
        char *next = strstr(comando, "\r\n");
        if (next)
        {
            *next = '\0'; //Dont move next yet.
        }
        if ( lenght <= 500 )
        {   
             if ( strncmp(comando, "HELO", 4) == 0)
             {     
                 //username = strtok((comando+4), "\r\n"); If I remember correctly, username is a 16 char string right after HELO. Right now, comando contains HELOusername\0\nnextcommand\r\n ... So you do not want a strtok on \r\n
                 username = comando+4;
                 if (strlen(username) > 16)
                 {
                      Writeline(fd, alert, strlen(alert));
                 }
                 Writeline(fd, passw, strlen(passw));
                 read(fd, password, MAX_LINE);  
                 passwd = strtok(password, "\r\n");
 
                 if (verify_login(username, passwd)==1)
                 {
                      auth=1;
                      Writeline(fd, good, strlen(good));
                 }
                 else if(verify_login(username, passwd)==-1)
                 {
                      auth=0;
                      Writeline(fd, fail, strlen(fail));
                 }  
           
		         
				 }  
				 
					
			 else if ( strncmp(comando, "LIST", 4) == 0)
				 {  
                      display_list(llist, fd);
                 }
  
              else if ( strncmp(comando, "QUIT", 4) == 0)
				 {  
                     Writeline(fd, bye, strlen(bye));
                     free(llist);
                     return;
                 }
		     
			 else if(strncmp(comando, "FIND", 4) == 0)
			    {    
                    if (auth == 0)
					{
                    Writeline(fd, noauth, strlen(noauth));
                    }
                   else {
                         if (llist->next == NULL )
						 {
                            Writeline(fd, noob, strlen(noob));
                         }
   
                         else	if (llist ->next != NULL )
						     {   
                                char * temp = comando+4;
                                short arr;
                                int val = 0;
    
                                do 
                                   {
                                     Writeline(fd, here, strlen(here));
	                                 memcpy(&arr, temp, 2);
                                     Writeline(fd, &arr, 2);
	                                 temp = temp + 2;
                                     val = ntohs(arr);
                                     search_value(llist, val, fd); 
	
                                    } while (val);
                               }
                           }
				 }
			 
			 
				
		   }
           if (next)
               comando = next+2; //move to next command here
           else
               comando = NULL; // could as well have used break here
         }
}    
 
//load the content in a linked list
 
void load_file_in_list(){
  
 llist = (struct NODE *)malloc(sizeof(struct NODE));
 llist->code = 0;
 llist->next = NULL;
 llist->size = 0;
 llist->line = 0;  
   
   FILE * pFile;
   char buffer [100];
   int code;
   char name[1000];
  
   
   pFile = fopen (objs_file , "r");
   if (pFile == NULL) perror ("Error opening file");
   else
   {
     while ( fgets (buffer , 100 , pFile) != NULL )
     {
       
	   sscanf(buffer,"%d %s \n", &code, name);
	   line++; // global variable
	   append_node(llist, name, code, line); /* insert values in the list */
	   size++;
	  }
	   fclose (pFile);
      }
 
}

           
         

Keywords: [C TCP server] Problem with Linked …

	Title
1	malloc
2	sizeof struct
3	sizeof with a struct
4	MALLOC
5	malloc, sizeof,
6	Sizeof()

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