select (Blocking I/O)

sever_select_tcp.cpp

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>

#define CONCURRENT 10

int main(){

	int listen_sock, conn_sock;
	struct sockaddr_in server;
	struct sockaddr_in client;
	fd_set fds, _fds;
	char rbuf[65535];
	char sbuf[] = "Done.";

	typedef struct {
		int sock_cnt;
		int sock_array[CONCURRENT];
	} conn_t;
	conn_t conn = { 0, {0} };

	listen_sock = socket(AF_INET, SOCK_STREAM, 0);
	if( listen_sock == -1 ){
		fprintf(stderr, "socket() error [%d].", errno);
		return -1;
	}

	server.sin_family = AF_INET;
	server.sin_addr.s_addr = inet_addr("127.0.0.1");
	server.sin_port = htons(11111);

	if( bind(listen_sock, (struct sockaddr *)&server, sizeof(server)) == -1 ){
		fprintf(stderr, "bind() error [%d].", errno);
		return -1;
	}

	if( listen(listen_sock, CONCURRENT) == -1 ){
		fprintf(stderr, "listen() error [%d].", errno);
		return -1;
	}

	FD_ZERO(&fds);
	FD_SET(listen_sock, &fds);

	int cnt=0;
	while(1){
		memcpy(&_fds, &fds, sizeof(fd_set));
	
		printf("Wait at select #%d.\n", cnt);

		int sock_max = listen_sock;
		for( int i=0; i<conn.sock_cnt; i++){
			printf("%d,",conn.sock_array[i]);
			sock_max = conn.sock_array[i]>sock_max?conn.sock_array[i]:sock_max;
		}
		printf("%d\n",listen_sock);

		if( select(sock_max+1, &_fds, NULL, NULL, NULL) == -1 ){
			fprintf(stderr,"select error [%d].", errno);
			return -1;
		}
	
		int len, size;
		if(FD_ISSET(listen_sock,&_fds)){
			printf("Connect request received.\n");

			len = sizeof(client);
			conn_sock = accept(listen_sock, (struct sockaddr *)&client, (socklen_t *)&len);
			if( conn_sock == -1 ){
				fprintf(stderr, "accept error [%d].", errno);
				return -1;
			}

			conn.sock_array[conn.sock_cnt] = conn_sock;
			conn.sock_cnt++;
			FD_SET(conn_sock,&fds);

		}else{
			printf("Send request received.\n");

			for(int i=0; i<conn.sock_cnt; i++){
				if(FD_ISSET(conn.sock_array[i],&_fds)){
					printf("Send client is %d.\n",conn.sock_array[i]);
					memset(rbuf, 0, sizeof(rbuf));

					size = recv(conn.sock_array[i], rbuf, sizeof(rbuf), 0);
					printf("Received data size %d byte.\n",size);
					if( size == -1){
						fprintf(stderr, "recv error [%d].", errno);
						return -1;
					}else if( size == 0 ){
						printf("Closed by %d.\n",conn.sock_array[i]);
						shutdown(conn.sock_array[i], 2);
						FD_CLR(conn.sock_array[i],&fds);
						for(int j=i; j<conn.sock_cnt-1; j++){
							conn.sock_array[j] = conn.sock_array[j+1];
						}
						conn.sock_cnt--;
					}else{
						printf("%s\n", rbuf);
						send(conn.sock_array[i], sbuf, sizeof(sbuf), 0);
					}

				}
			}

		}

		sleep(1);
		cnt++;
	}

	return 0;

}