Multithreaded HTTP Server for Linux built up by the pool of threads utilizing select()system call.
Developing code bellow we follow general guidelines from [1] chapter 11.
The only one source file has been modified is server.c.Instead of fork new process to handle each incoming client's connection, as procedure server_run ( ) does in [1], we start pool of 1024 threads accepting as parameter descriptor of passive socket.The procedure run by each thread is asynchronous BSD socket’s server utilizing select() system
call (see for example [2],chapter 13(5)) to switch between handling incoming client's requests by accept() system call
and receiving "http" requests from clients already connected to server utilizing procedures handle_request() and
handle_get() from [1],chapter 11.
References.
1.Mark Mitchel,Jeffrey Oldham,Alex Samuel. Advanced Linux Programming.
New Riders Publishing , 2001. www.advancedlinuxprogramming.com
2.Douglas E. Comer,David L. Stevens Internet Working with TCP/IP ,vol 3
Client-Server Programming and application Linux/Posix Socket Version,Prentice Hall,Inc. 2001
/*
* server.c module :- multithreaded version, starting pool of threads,
* multiplexing select() system call, to serve new connections
* utilizing accept() system call and "http" responds for clients
* already connected to server simultaneously.
*/
#include <arpa/inet.h>
#include <assert.h>
#include <errno.h>
#include <netinet/in.h>
#include <signal.h>
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <unistd.h>
#include <pthread.h>
#include "server.h"
#define NUM_THREADS 1024
pthread_mutex_t get_mutex=PTHREAD_MUTEX_INITIALIZER;
static char* not_found_response_template =
"HTTP/1.0 404 Not Found\n"
"Content-type: text/html\n"
"\n"
"<html>\n"
" <body>\n"
" <h1>Not Found</h1>\n"
" <p>The requested URL %s was not found on this server.</p>\n"
" </body>\n"
"</html>\n";
static char* bad_method_response_template =
"HTTP/1.0 501 Method Not Implemented\n"
"Content-type: text/html\n"
"\n"
"<html>\n"
" <body>\n"
" <h1>Method Not Implemented</h1>\n"
" <p>The method %s is not implemented by this server.</p>\n"
" </body>\n"
"</html>\n";
static char* ok_response =
"HTTP/1.0 200 OK\n"
"Content-type: text/html\n"
"\n";
static char* bad_request_response =
"HTTP/1.0 400 Bad Request\n"
"Content-type: text/html\n"
"\n"
"<html>\n"
" <body>\n"
" <h1>Bad Request</h1>\n"
" <p>This server did not understand your request.</p>\n"
" </body>\n"
"</html>\n";
void
die(const char *func, int err)
{
fprintf(stderr,"%s: %s\n",func,strerror(err));
abort();
}
static void handle_get (int connection_fd, const char* page)
{
struct server_module* module = NULL;
if (*page == '/' && strchr (page + 1, '/') == NULL) {
char module_file_name[64];
snprintf (module_file_name, sizeof (module_file_name),
"%s.so", page + 1);
module = module_open (module_file_name);
}
if (module == NULL) {
char response[1024];
snprintf (response, sizeof (response), not_found_response_template, page);
write (connection_fd, response, strlen (response));
}
else {
write (connection_fd, ok_response, strlen (ok_response));
(*module->generate_function) (connection_fd);
module_close (module);
}
}
static void *
handle_connection (int fdSock)
{
int connection_fd = fdSock;
char buffer[256];
ssize_t bytes_read;
bytes_read = read (connection_fd, buffer, sizeof (buffer) - 1);
if (bytes_read > 0) {
char method[sizeof (buffer)];
char url[sizeof (buffer)];
char protocol[sizeof (buffer)];
buffer[bytes_read] = '\0';
sscanf (buffer, "%s %s %s", method, url, protocol);
while (strstr (buffer, "\r\n\r\n") == NULL)
bytes_read = read (connection_fd, buffer, sizeof (buffer));
if (bytes_read == -1) {
close (connection_fd);
return;
}
if (strcmp (protocol, "HTTP/1.0") && strcmp (protocol, "HTTP/1.1")) {
write (connection_fd, bad_request_response,
sizeof (bad_request_response));
}
else if (strcmp (method, "GET")) {
char response[1024];
snprintf (response, sizeof (response),
bad_method_response_template, method);
write (connection_fd, response, strlen (response));
}
else
handle_get (connection_fd, url);
}
else if (bytes_read == 0)
;
else {
system_error ("read");
}
close(connection_fd);
}
void *
serv_request(void *insock)
{
int msock = (int)insock;
struct sockaddr_in fsin;
fd_set rfds;
fd_set afds;
unsigned int alen;
int fd,nfds;
int rval;
socklen_t address_length;
struct sockaddr_in socket_address;
nfds=getdtablesize();
FD_ZERO(&afds);
FD_SET(msock,&afds);
while(1) {
memcpy(&rfds,&afds,sizeof(rfds));
if (select(nfds,&rfds,(fd_set *)0,(fd_set *)0,(struct timeval *)0) < 0)
die("select()",errno);
if (FD_ISSET(msock,&rfds)) {
int ssock;
alen=sizeof(fsin);
/*
Serving new incoming client's connection
*/
pthread_mutex_lock(&get_mutex);
ssock=accept(msock,(struct sockaddr *)&fsin,&alen);
pthread_mutex_unlock(&get_mutex);
if (ssock < 0)
die ("accept()",errno);
if (verbose) {
socklen_t address_length;
address_length = sizeof (socket_address);
rval = getpeername (ssock, &socket_address, &address_length);
assert (rval == 0);
printf ("Thread '%d' accepted connection from %s\n",
pthread_self(),inet_ntoa (socket_address.sin_addr));
}
FD_SET(ssock,&afds);
}
for (fd=0;fd < nfds; ++fd)
if (fd != msock && FD_ISSET(fd,&rfds)) {
printf("Thread '%d' responding request...\n",pthread_self());
/*
Serving client had been already connected to server
*/
handle_connection(fd);
FD_CLR(fd,&afds);
}
}
}
void
server_run(struct in_addr local_address,uint16_t port)
{
struct sockaddr_in socket_address;
int rval;
int server_socket;
int k;
/*
Getting socket's descriptor to be passed to
each thread in the pool
*/
server_socket = socket (PF_INET, SOCK_STREAM, 0);
if (server_socket == -1)
system_error ("socket");
memset (&socket_address, 0, sizeof (socket_address));
socket_address.sin_family = AF_INET;
socket_address.sin_port = port;
socket_address.sin_addr = local_address;
rval = bind (server_socket, &socket_address, sizeof (socket_address));
if (rval != 0)
system_error ("bind");
rval = listen (server_socket, 10);
if (rval != 0)
system_error ("listen");
if (verbose) {
socklen_t address_length;
address_length = sizeof (socket_address);
rval = getsockname (server_socket, &socket_address, &address_length);
assert (rval == 0);
printf ("server listening on %s:%d\n",
inet_ntoa (socket_address.sin_addr),
(int) ntohs (socket_address.sin_port));
}
/*
Starting pool of threads building up HTTP server
*/
size_t stacksize;
pthread_t p_thread[NUM_THREADS];
pthread_attr_t attr;
pthread_attr_init(&attr);
stacksize = 500000;
pthread_attr_setstacksize (&attr, stacksize);
pthread_attr_getstacksize (&attr, &stacksize);
for(k=0; k<NUM_THREADS; k++){
pthread_create(&p_thread[k],&attr,serv_request,(void*)server_socket);
}
pthread_attr_destroy(&attr);
for(k=0;k<NUM_THREADS;k++) {
pthread_join(p_thread[k], NULL);
printf("Completed join with thread %d\n",k);
}
}
