Socket编程实践(4) --多进程并发server
1.Socket地址复用
int getsockopt(int sockfd, int level, int optname, void *optval, socklen_t *optlen); int setsockopt(int sockfd, int level, int optname, const void *optval, socklen_t optlen);
服务端尽可能使用SO_REUSEADDR,在绑定之前尽可能调用setsockopt来设置SO_REUSEADDR套接字选项。该选项可以使得server不必等待TIME_WAIT状态消失就可以重启服务器(对于TIME_WAIT状态会在后面续有叙述).
可以在bind之前添加代码(完整代码请参照博文最后):
int on = 1; if (setsockopt(listenfd,SOL_SOCKET,SO_REUSEADDR, &on,sizeof(on)) == -1) err_exit("setsockopt SO_REUSEADDR error");
用以支持地址复用.
2.process-per-connecton
我们的echo服务器最大的缺点就是无法支持多客户连接,即使客户端能够连接到服务器上(client端connect时并没有出错返回), 服务器也不为该客户做服务,(直接没什么反应),虽然链接是有的(也就是说,客户端是已经连接到服务器上的了,但是服务器就是不搭理你....), 我们提出的改进方案是process-per-connection(一条连接一个进程, 我们在多线程那一章中曾经提出过一条连接一个线程, 这种方案相比较而言能够比多进程拥有更高的并发量);
/** 示例:echo server改进, 多进程模型(client并未更改)**/ void echo(int clientfd); int main() { int listenfd = socket(AF_INET, SOCK_STREAM, 0); if (listenfd == -1) err_exit("socket error"); int on = 1; if (setsockopt(listenfd,SOL_SOCKET,SO_REUSEADDR, &on,sizeof(on)) == -1) err_exit("setsockopt SO_REUSEADDR error"); struct sockaddr_in addr; addr.sin_family = AF_INET; addr.sin_port = htons(8001); addr.sin_addr.s_addr = htonl(INADDR_ANY); if (bind(listenfd, (const struct sockaddr *)&addr, sizeof(addr)) == -1) err_exit("bind error"); if (listen(listenfd, SOMAXCONN) == -1) err_exit("listen error"); struct sockaddr_in clientAddr; //谨记: 此处一定要初始化 socklen_t addrLen = sizeof(clientAddr); while (true) { int clientfd = accept(listenfd, (struct sockaddr *)&clientAddr, &addrLen); if (clientfd == -1) err_exit("accept error"); //打印客户IP地址与端口号 cout << "Client information: " << inet_ntoa(clientAddr.sin_addr) << ", " << ntohs(clientAddr.sin_port) << endl; pid_t pid = fork(); if (pid == -1) err_exit("fork error"); else if (pid > 0) close(clientfd); //子进程处理链接 else if (pid == 0) { close(listenfd); echo(clientfd); //子进程一定要exit, 否则的话, 该子进程也会回到accept处 exit(EXIT_SUCCESS); } } close(listenfd); } void echo(int clientfd) { char buf[512] = {0}; int readBytes; while ((readBytes = read(clientfd, buf, sizeof(buf))) > 0) { cout << buf; if (write(clientfd, buf, readBytes) == -1) err_exit("write socket error"); memset(buf, 0, sizeof(buf)); } if (readBytes == 0) { cerr << "client connect closed..." << endl; close(clientfd); } else if (readBytes == -1) err_exit("read socket error"); }
完整代码实现:
http://download.csdn.net/detail/hanqing280441589/8458053
3. P2P聊天程序设计与实现
server端与client都有两个进程:
(1)父进程负责从socket中读取数据将其写至终端, 由于父进程使用的是read系统调用的阻塞版本, 因此如果socket中没有数据的话, 父进程会一直阻塞; 如果read返回0, 表示对端连接关闭, 则父进程会发送SIGUSR1信号给子进程, 通知其退出;
(2)子进程负责从键盘读取数据将其写入socket, 如果键盘没有数据的话, 则fgets调用会一直阻塞;
//serever端代码与说明 int main() { int listenfd = socket(AF_INET, SOCK_STREAM, 0); if (listenfd == -1) err_exit("socket error"); int on = 1; if (setsockopt(listenfd,SOL_SOCKET,SO_REUSEADDR, &on,sizeof(on)) == -1) err_exit("setsockopt SO_REUSEADDR error"); struct sockaddr_in addr; addr.sin_family = AF_INET; addr.sin_port = htons(8001); addr.sin_addr.s_addr = htonl(INADDR_ANY); if (bind(listenfd, (const struct sockaddr *)&addr, sizeof(addr)) == -1) err_exit("bind error"); if (listen(listenfd, SOMAXCONN) == -1) err_exit("listen error"); struct sockaddr_in clientAddr; socklen_t addrLen = sizeof(clientAddr); int clientfd = accept(listenfd, (struct sockaddr *)&clientAddr, &addrLen); if (clientfd == -1) err_exit("accept error"); close(listenfd); //打印客户IP地址与端口号 cout << "Client information: " << inet_ntoa(clientAddr.sin_addr) << ", " << ntohs(clientAddr.sin_port) << endl; char buf[512] = {0}; pid_t pid = fork(); if (pid == -1) err_exit("fork error"); //父进程: socket -> terminal else if (pid > 0) { int readBytes; while ((readBytes = read(clientfd, buf, sizeof(buf))) > 0) { cout << buf; memset(buf, 0, sizeof(buf)); } if (readBytes == 0) cout << "client connect closed...\nserver exiting..." << endl; else if (readBytes == -1) err_exit("read socket error"); //通知子进程退出 kill(pid, SIGUSR1); } //子进程: keyboard -> socket else if (pid == 0) { signal(SIGUSR1, sigHandler); while (fgets(buf, sizeof(buf), stdin) != NULL) { if (write(clientfd, buf, strlen(buf)) == -1) err_exit("write socket error"); memset(buf, 0, sizeof(buf)); } } close(clientfd); exit(EXIT_SUCCESS); }
//client端代码与说明 int main() { int sockfd = socket(AF_INET, SOCK_STREAM, 0); if (sockfd == -1) err_exit("socket error"); //填写服务器端口号与IP地址 struct sockaddr_in serverAddr; serverAddr.sin_family = AF_INET; serverAddr.sin_port = htons(8001); serverAddr.sin_addr.s_addr = inet_addr("127.0.0.1"); if (connect(sockfd, (const struct sockaddr *)&serverAddr, sizeof(serverAddr)) == -1) err_exit("connect error"); char buf[512] = {0}; pid_t pid = fork(); if (pid == -1) err_exit("fork error"); //父进程: socket -> terminal else if (pid > 0) { int readBytes; while ((readBytes = read(sockfd, buf, sizeof(buf))) > 0) { cout << buf; memset(buf, 0, sizeof(buf)); } if (readBytes == 0) cout << "server connect closed...\nclient exiting..." << endl; else if (readBytes == -1) err_exit("read socket error"); kill(pid, SIGUSR1); } //子进程: keyboard -> socket else if (pid == 0) { signal(SIGUSR1, sigHandler); while (fgets(buf, sizeof(buf), stdin) != NULL) { if (write(sockfd, buf, strlen(buf)) == -1) err_exit("write socket error"); memset(buf, 0, sizeof(buf)); } } close(sockfd); exit(EXIT_SUCCESS); }
完整代码实现:
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