Multithreaded Server in LInux - c

Question

I am Working on server Programming in C in Linux environment.At same time there might be several clients linked with the Server.It's my first project on server Programming and not having much experience in Multi-threading.Till Now i have Programmed following for Multithreading.
I want to get some idea about following Points.
1.How many clients will the server Handle?
2.will pthread_t thr;create multiple Threads or i need to do something like pthread_t thr[X] to create X Threads ?
3.How can i get the data for each client in the following code ?
4.Will pthread_create create a new copy of *connection_handler for each new client connected.
void dieWithError(char *errormsg);
FILE *file;
void *connection_handler(void *socket_desc)
{
//Get the socket descriptor
int sock = *(int*)socket_desc;
int read_size;
char *message , client_message[2000];
//Receive a message from client
while( (read_size = recv(sock , client_message , 2000 , 0)) > 0 )
{
//end of string marker
client_message[read_size] = '\0';
printf("%s",client_message);
fprintf(file,"%s", client_message);
//clear the message buffer
memset(client_message, 0, 2000);
}
if(read_size == 0)
{
puts("Client disconnected");
fflush(stdout);
}
else if(read_size == -1)
{
perror("recv failed");
}
return 0;
}
int main(int argc, char** argv) {
int sock_desc = 0, connfd = 0,listenfd =0;
struct sockaddr_in serv_addr;
int clntSock;
struct sockaddr_in echoClntAddr;
unsigned int clntLen;
char sendBuff[1025];
char recvBuff[10025];
int n = 0;
pthread_t thr;
sock_desc = socket(AF_INET, SOCK_STREAM, 0);
if(sock_desc < 0 )
dieWithError("Unable to open Socket\n");
memset(&serv_addr,0,sizeof(serv_addr));
serv_addr.sin_family = AF_INET ;
serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
serv_addr.sin_port = htons(7024);
if(bind(sock_desc, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0)
dieWithError("bind failed\n");
if(listen(sock_desc,3) < 0)
dieWithError("listen failed\n");
file = fopen("testServer.txt", "w");
clntSock = sizeof(struct sockaddr);
int i =0;
while((connfd = accept(sock_desc, (struct sockaddr *)&echoClntAddr,(socklen_t*)&clntSock)))
{
puts("Connection accepted");
if( pthread_create( &thr, NULL , connection_handler , (void*) &connfd) < 0)
{
perror("could not create thread");
return 1;
}
//Now join the thread , so that we dont terminate before the thread
//pthread_join( thread_id , NULL);
puts("Handler assigned");
}
if (connfd < 0)
{
perror("accept failed");
return 1;
}
return (EXIT_SUCCESS);
}
void dieWithError(char *errormsg){
printf("%s", errormsg);
}

Answer 1

It depends on the server machine, and how many threads it can handle. Generally speaking, the more threads you have, the more time the operating system will spend just switching between threads meaning the threads themselves will have less time doing any real work.
E.g. pthread_t thr; is a single variable, able to hold a single thread. You can reuse it for multiple threads, but then you loose the other threads leading to a resource leak. You probably need an array or a list if you want multiple threads.
Structures. One structure per thread, each structure containing the thread information (pthread_t), the client socket, and everything else needed by both the main thread and the client-handling thread.
No. connection_handler is a function, there will only be one instance of a function per process in memory, functions are not copied.