Socket 單執行緒多使用者併發的兩個小例子
阿新 • • 發佈：2019-02-19
#include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <errno.h> #include <string.h> #include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> #include <arpa/inet.h> #define MYPORT 1234 // the port users will be connecting to #define BACKLOG 5 // how many pending connections queue will hold #define BUF_SIZE 200 int fd_A[BACKLOG]; // accepted connection fd int conn_amount; // current connection amount void showclient() { int i; printf("client amount: %d\n", conn_amount); for (i = 0; i < BACKLOG; i++) { printf("[%d]:%d ", i, fd_A[i]); } printf("\n\n"); } int main(void) { int sock_fd, new_fd; // listen on sock_fd, new connection on new_fd struct sockaddr_in server_addr; // server address information struct sockaddr_in client_addr; // connector's address information socklen_t sin_size; int yes = 1; char buf[BUF_SIZE]; int ret; int i; if ((sock_fd = socket(AF_INET, SOCK_STREAM, 0)) == -1) { perror("socket"); exit(1); } if (setsockopt(sock_fd, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(int)) == -1) { perror("setsockopt"); exit(1); } server_addr.sin_family = AF_INET; // host byte order server_addr.sin_port = htons(MYPORT); // short, network byte order server_addr.sin_addr.s_addr = INADDR_ANY; // automatically fill with my IP memset(server_addr.sin_zero, '\0', sizeof(server_addr.sin_zero)); if (bind(sock_fd, (struct sockaddr *)&server_addr, sizeof(server_addr)) == -1) { perror("bind"); exit(1); } if (listen(sock_fd, BACKLOG) == -1) { perror("listen"); exit(1); } printf("listen port %d\n", MYPORT); fd_set fdsr; int maxsock; struct timeval tv; conn_amount = 0; sin_size = sizeof(client_addr); maxsock = sock_fd; while (1) { // initialize file descriptor set FD_ZERO(&fdsr); FD_SET(sock_fd, &fdsr); // timeout setting tv.tv_sec = 30; tv.tv_usec = 0; // add active connection to fd set for (i = 0; i < BACKLOG; i++) { if (fd_A[i] != 0) { FD_SET(fd_A[i], &fdsr); } } ret = select(maxsock + 1, &fdsr, NULL, NULL, &tv); if (ret < 0) { perror("select"); break; } else if (ret == 0) { printf("timeout\n"); continue; } // check every fd in the set for (i = 0; i < conn_amount; i++) { if (FD_ISSET(fd_A[i], &fdsr)) { ret = recv(fd_A[i], buf, sizeof(buf), 0); if (ret <= 0) { // client close printf("client[%d] close\n", i); close(fd_A[i]); FD_CLR(fd_A[i], &fdsr); fd_A[i] = 0; } else { // receive data if (ret < BUF_SIZE) memset(&buf[ret], '\0', 1); printf("client[%d] send:%s\n", i, buf); } } } // check whether a new connection comes if (FD_ISSET(sock_fd, &fdsr)) { new_fd = accept(sock_fd, (struct sockaddr *)&client_addr, &sin_size); if (new_fd <= 0) { perror("accept"); continue; } // add to fd queue if (conn_amount < BACKLOG) { fd_A[conn_amount++] = new_fd; printf("new connection client[%d] %s:%d\n", conn_amount, inet_ntoa(client_addr.sin_addr), ntohs(client_addr.sin_port)); if (new_fd > maxsock) maxsock = new_fd; } else { printf("max connections arrive, exit\n"); send(new_fd, "bye", 4, 0); close(new_fd); break; } } showclient(); } // close other connections for (i = 0; i < BACKLOG; i++) { if (fd_A[i] != 0) { close(fd_A[i]); } } exit(0); }
下面這個對比如客戶端突然斷電，拔掉網線等（這個時候，服務端是檢測不到的客戶端已斷開）特殊情況進行了判斷，從而有效斷開連線。
void run() { char msg[BUF_SIZE]; int Listen_socket,ret,on; struct sockaddr_in local_addr; struct sockaddr_in client_addr; int i; fd_set fdsr; //檔案描述符集的定義 socklen_t addr_size; addr_size = sizeof(struct sockaddr_in); int conn_amount = 0; //當前最大活躍連線數 int new_fd; struct timeval tv; //建立socket套接字 if( (Listen_socket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) == -1) { emit err_msg_signal("failed create socket"); } //bind API 函式將允許地址的立即重用 on = 1; ret = setsockopt( Listen_socket, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on) ); int nNetTimeout=2000;//2秒 //設定傳送時限 setsockopt(Listen_socket,SOL_SOCKET,SO_SNDTIMEO,(char *)&nNetTimeout,sizeof(int) ); //設定接收時限 setsockopt(Listen_socket,SOL_SOCKET,SO_RCVTIMEO,(char *)&nNetTimeout,sizeof(int)); //設定本機服務型別 local_addr.sin_family = AF_INET; local_addr.sin_port = htons(port); local_addr.sin_addr.s_addr = INADDR_ANY; //while(flag_port == 0) //繫結本機IP和埠號 if(bind(Listen_socket, (struct sockaddr*)&local_addr, sizeof(struct sockaddr)) == -1) { emit err_msg_signal("failed bind"); } //監聽客戶端連線 if(listen(Listen_socket, 8) == -1) { emit err_msg_signal("failed listen"); } QTime current_time; current_time = QTime::currentTime(); int flag_minutechange = 0,lastminute = current_time.currentTime().minute(); int maxsock = Listen_socket; /*************************************** 以下為併發連線處理，系統關鍵部分 ***************************************/ while (1) { if( current_time.currentTime().minute() != lastminute) //每次迴圈開始都讀取系統時間，與上次分鐘數比較，為以下超時判斷提供依據 { lastminute = current_time.currentTime().minute(); flag_minutechange = 1; } FD_ZERO(&fdsr); //每次進入迴圈都重建描述符集 FD_SET(Listen_socket, &fdsr); for (i = 0; i < MAXCLIENT; i++) //將存在的套接字加入描述符集 { if (fd[i] != 0) { FD_SET(fd[i], &fdsr); if(flag_minutechange == 1) { con_time[i]--; if(con_time[i] <= 0) { close(fd[i]); FD_CLR(fd[i], &fdsr); fd[i] = 0; conn_amount--; } } } } flag_minutechange = 0; tv.tv_sec = 1; tv.tv_usec = 0; ret = select(maxsock + 1, &fdsr, NULL, NULL,&tv); //關鍵的select()函式，用來探測各套接字的異常 //如果在檔案描述符集中有連線請求或傳送請求，會作相應處理， //從而成功的解決了單執行緒情況下阻塞程序的情況，實現多使用者連線與通訊 if (ret < 0) //<0表示探測失敗 { qDebug()<<"failed select\n"; break; } else if (ret == 0) //=0表示超時，下一輪迴圈 { //qDebug()<<"timeout\n"; continue; } // 如果select發現有異常，迴圈判斷各活躍連線是否有資料到來 for (i = 0; i < conn_amount; i++) { if (FD_ISSET(fd[i], &fdsr)) { ret = recv(fd[i], msg, BUF_SIZE, 0); if (ret <= 0) // recv<=0,表明客戶端關閉連線，伺服器也關閉相應連線，並把連線套接子從檔案描述符集中清除 { qDebug("client[%d] close\n", i); close(fd[i]); FD_CLR(fd[i], &fdsr); fd[i] = 0; conn_amount--; } else //否則表明客戶端有資料傳送過來，作相應接受處理 { con_time[i] = MAX_IDLECONNCTIME; //重新寫入fd[i]的超時數，再此之後如果MAX_IDLECONNCTIME分鐘內此連線無反應，伺服器會關閉該連線 if (ret < BUF_SIZE) emit err_msg_signal("client ip: " + QString::fromLatin1(inet_ntoa(client_addr.sin_addr)) + " port: " + QString::number(ntohs(client_addr.sin_port))+" coming data"); qDebug("client[%d] send:%s\n", i, msg); msg[ret] = '\0'; emit recv_msg_signal(QString::fromLatin1(msg),fd[i]); //send(fd[i],msg,ret,0); } } } // 以下說明異常有來自客戶端的連線請求 if (FD_ISSET(Listen_socket, &fdsr)) { new_fd = accept(Listen_socket, (struct sockaddr *)&client_addr, &addr_size); if (new_fd <= 0) { qDebug("failed accept"); continue; } // 判斷活躍連線數時候是否小於最大連線數，如果是，新增新連線到檔案描述符集中 if (conn_amount < MAXCLIENT) { for(i = 0;i < MAXCLIENT;i++) { if(fd[i] == 0) { fd[i] = new_fd; con_time[i] = MAX_IDLECONNCTIME; //每次新建立連線，設定該連線的超時數，如果此連線此後MAX_IDLECONNCTIME分鐘內無反應，關閉該連線 break; } } conn_amount++; //fd[conn_amount++] = new_fd; qDebug("new connection client[%d] %s:%d\n", conn_amount, inet_ntoa(client_addr.sin_addr), ntohs(client_addr.sin_port)); emit err_msg_signal("client ip: " + QString::fromLatin1(inet_ntoa(client_addr.sin_addr)) + " port: " + QString::number(ntohs(client_addr.sin_port))); if (new_fd > maxsock) maxsock = new_fd; } else { qDebug("MAXCLIENT arrive, exit\n"); send(new_fd, "over MAXCLIENT\n", 25, 0); close(new_fd); continue; } } } }