How to use IO multiplexing technology to improve server concurrency performance? - c

Question

I want to make a server software similar to Apache on windows platforms.
. The client sends data to the specified server port and the server responds accordingly. In order to improve the client access speed, I want to use "select" to improve the performance of the server, but there are many problems in the use process.
Here is my code;
Function "create_server"
This function is used to create the server Socket and set it to non-blocking.
int create_server(char*ip_address,int port) {
WORD sockVersion = MAKEWORD(2, 2);
WSADATA wsaData;
if(WSAStartup(sockVersion, &wsaData) != 0)
{
return 0;
}
int server_socket = socket(AF_INET,SOCK_STREAM, IPPROTO_TCP);
int ret = -1;
struct sockaddr_in addr;
if (server_socket == -1) {
return -1;
}
memset(&addr, 0, sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_port = htons(port);
addr.sin_addr.S_un.S_addr= INADDR_ANY;
ret = bind(server_socket,(LPSOCKADDR)&addr,sizeof(addr));
if (ret == -1) {
perror("bind error！");
return -2;
}
listen(server_socket,5);
SetBlock(server_socket, 0);
return server_socket;}
Function "SetBlock"
This function is used to change the socket blocking mode.
int SetBlock(int sock, int isblock){
int re = 0;
unsigned long ul = 0;
if (!isblock) ul = 1;
re = ioctlsocket(sock, FIONBIO, (unsigned long*)& ul);
if (re != 0) return 0;
return 1;
}
Function "main"
int main() {
int s = create_server("127.0.0.1",6666);
int client_socket = -1;
struct sockaddr_in clientaddr;
int addrlen = sizeof(clientaddr);
char buf[1025];
int buffersize=1,result=0;
int isread = 0;
fd_set server;
struct timeval timeout;
int fd = 0;
timeout.tv_sec = 3;
timeout.tv_usec = 0;
FD_ZERO(&server);
FD_SET(s, &server);
while (1) {
result = select(FD_SETSIZE, &server, NULL, NULL, NULL);
if (result < 1) {
perror("error！");
exit(1);
}
if (FD_ISSET(s, &server)) {
//if server can be readable and written do this
client_socket = accept(s, (struct sockaddr*) & clientaddr, &addrlen);
while (buffersize > 0) {
buffersize = recv(client_socket, buf, 1024, 0);
buf[buffersize] = '\0';
printf("%s", buf);
if (buffersize < 1024) {
break;
}
}
buffersize = 1;
}
}
return 0;}
As you know, TCP takes some time to establish a connection. I want to use the "select" function to reduce the setup time of multi-client connections. I think the function "accept" is the process of establishing connection between client and server, but how to use IO multiplexing in this process, please help me.

Answer 1

the use of select() will delay all client connections to the server.
suggest a sequence similar to:
create a thread pool
create a sockaddr_in
sock_t serverSock = socket()
bind()
listen()
while( 1 )
{
sock_t clientSock = accept( serverSock, ... )
pass clientSock to available thread and mark thread as 'busy'
}
That way, the communication with a client does not 'hang' on a select(), nor a accept()
in each thread:
while(1)
{
wait until thread marked as 'busy'
sock_t mySocket = passedSocket
perform all communication with the specific client
close( mySocket );
mark thread as 'idle'
}