c - 如何利用IO复用技术提高服务器并发性能？

Question

我想在windows平台上做一个类似Apache的服务器软件。。客户端向服务器指定端口发送数据，服务器做出相应响应。为了提高客户端访问速度，想用“select”来提高服务器的性能，但是在使用过程中出现了很多问题。这是我的代码；

函数“创建服务器”

该函数用于创建服务器Socket并将其设置为非阻塞。

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;}

函数“SetBlock”

该函数用于改变socket阻塞模式。

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;
}

函数“主”

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;}

如您所知，TCP 需要一些时间来建立连接。我想使用“选择”功能来减少多客户端连接的建立时间。我认为“accept”函数是客户端和服务器建立连接的过程，但是这个过程中如何使用IO复用，请帮助我。

Answer 1

使用select()将延迟所有客户端与服务器的连接。

建议类似于以下的序列:

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'
}

这样，与客户端的通信不会“挂起”在 select() 上，也不会“挂起”在 accept()

上

在每个线程中:

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'
}