Server doesn't alloc a thread for every new client (sockets) - c

Question

I made a small program server client using sockets. I'll will explain what it needs to do and then the bug.
Application has a server witch wait's for clients. It supports max 6 clients at the same time. For each client server launch a thread in DETASH_STATE and then it come back and listen.
A client will submit the context of a file to the server. (i chose to send line by line)
The server will receive the content sent by a client and save it into a file, with a unique name like: __ft_"Any random string".txt
I hope all is clear till now.
The bug:
Well if i launch the client let say 20 times. On server side i don't have 20 files. Sometimes i have 10, sometimes 12,5,7(unpredictable). It writes in a single file the content sent by 3 or 4 or 5 clients ( here i need to have 3-4-5 files). I don't get where is the bug or what i made wrong. If you need additional information please tell me.
This is the server code (a part of it):
/**********ASSING A PROTOCOL TO A SOCKET (BIND)************/
if(bind(sock_dest, (struct sockaddr *)&server,sizeof (server))<0)
{
printf("Bind failed\n");
return 1;
}
/**********************************************************/
/*************** LISTEN FOR CONNECTIONS ********************/
listen(sock_dest,6);
printf("Waiting for connections\n");
/**********************************************************/
/****ACCEPT CONNECTION AND MAKE ATHREAD FOR EVERY CLIENT***/
c = sizeof ( struct sockaddr_in);
pthread_t thread_id;
pthread_attr_t attr;
pthread_attr_init(&attr);
pthread_attr_setdetachstate(&attr,PTHREAD_CREATE_DETACHED);
while( ( client_socket = accept( sock_dest, ( struct sockaddr *)&client, (socklen_t *) &c)) )
{
printf("Connection accepted.\n");
if(client_socket < 0)
{
printf("Accepting connection failed.\n");
return 1;
}
if(pthread_create( &thread_id, &attr, connection_handler, (void*) &client_socket ) < 0)
{
printf("Couldn't create a thread for the new client.\n");
return 1;
}
else
printf("Handler assigned\n");
}
return 0;
}
void *connection_handler (void *socket_dest)
{
char *dest_file_name;
char buffer[300];
int sock = *( int *) socket_dest;
char *exit_signal="EXIT";
if((dest_file_name=create_random_name())==NULL)
{
printf("Generating a random name failed\n");
return NULL;
}
int i=0;
while(1)
{
while(i<299)
{
recv(sock,buffer+i,1,0);
if(buffer[i]=='\n')
{
i=0; // setting i to 0 because next time when we read a path(string) it need to be stored from 0 pozition in array.
break;
}
++i;
}
if((strcmp(buffer,exit_signal))==0)
{
printf("Exit signal received.\n");
return NULL;
}
if((write_line_in_file(buffer,dest_file_name))==1)
{
printf("Failed to write one of the lines in %s\n",dest_file_name);
}
printf("Linie primita:%s\n",buffer);
bzero(buffer,256); // put all bytes to 0 from buffer
}
return 0;
}
char *create_random_name(void)
{
const char charset[] = "abcdefghijklmnopqrstuvwxyz";
char *file_name;
int i=0;
int key;
struct stat stbuf;
time_t t;
while(1)
{
srand((unsigned) time(&t));
if((file_name = malloc(16 * sizeof ( char )) ) == NULL)
{
printf("Failed to alloc memory space\n");
return NULL;
}
strcpy(file_name,"__ft_");
for(i=5 ; i<11 ; i++)
{
key = rand() % (int)(sizeof(charset)-1);
file_name[i]=charset[key];
}
strcat(file_name,".txt");
file_name[15] = '\0';
if(stat(file_name,&stbuf)==-1)
{
break;
}
}
return file_name;
}
/************* RETURN 0 IF SUCCES AND 1 IF FAILS ***********/
int write_line_in_file(char *line,char *file_name)
{
FILE *file;
if((file=fopen(file_name, "a")) == NULL)
{
printf("Can't open %s.\n");
return 1;
}
fprintf(file,"%s",line);
fclose(file);
return 0;
}
And this is the client code (i don't think here is the problem):
#include <stdio.h>
#include <stdlib.h>
#include<netdb.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <string.h>
int main(int argc, char *argv[])
{
/***************CHECKING THE ARGUMENT*************/
if (argc < 2)
{
printf("Usage: %s hostname\n", argv[0]);
return 1;
}
/*************************************************/
int sock_dest;
struct sockaddr_in server_addr;
char line[300];
/******************CREATE SOCKET*****************/
sock_dest = socket(AF_INET, SOCK_STREAM, 0);
if(sock_dest == -1)
{
printf("Couldn't create socket.\n");
return 1;
}
struct hostent *server;
server = gethostbyname(argv[1]);
if (server == NULL)
{
printf("ERROR, no such host\n");
return 1;
}
/***** SETTING FIELDS OF SERVER SOCKADDR_IN STRUCTURE *****/
bzero((char *) &server_addr, sizeof(server_addr));
server_addr.sin_family = AF_INET;
bcopy((char *)server->h_addr,(char *)&server_addr.sin_addr.s_addr,server->h_length);
server_addr.sin_port = htons ( 31000 );
/**********************************************************/
/*********TRYING TO CONNECT TO THE SERVER******************/
if (connect(sock_dest,(struct sockaddr *) &server_addr,sizeof(server_addr)) < 0)
{
printf("ERROR:(Can't connect to the server. Please check if it's online)\n");
return 1;
}
/***********************************************************/
char path_read[200];
int read_len,n;
FILE *f_read;
char *exit_signal = "\nEXIT\0";
if((f_read=fopen("test.txt","r"))==NULL)
{
printf("Failed to open path.txt.\n");
return 0;
}
while((fgets(path_read,200,f_read))!=NULL)
{
path_read[strlen(path_read)+1]='\n';
n = write(sock_dest,path_read,strlen(path_read));
if(n<0)
error("ERROR writing to socket");
bzero(path_read,200);
}
n=write(sock_dest,exit_signal,strlen(exit_signal));
fclose(f_read);
close(sock_dest);
printf("All lines in the file were sent to the server.\nExiting...\n");
return 0;
}

Answer 1

This is one bug:
(void*) &client_socket
Firstly, no need to cast to void*. Secondly, it looks like client_socket is a local variable, who's address you pass to the thread as context. In the starting thread, you then continue to overwrite its value with the next iteration.