使用了fork、select、epoll三种socket服务器工作模式，客户端向服务端发送任何数据，服务端再原样返回给客户端，本文的目的只为加深偶的记忆。
fork:每accept到一个socket之后，开启一个子进程来负责收发处理工作。
select:监控文件描述符事件
epoll:监控文件描述符事件，比select性能优异，可最大支持2W个连接，有死连接时处理能力高
文末附注了SOCKET的一些常见错误标识
-------------------------- fork.cpp --------------------------
#include <sys/types.h> #include <sys/socket.h> #include <sys/wait.h> #include <arpa/inet.h> #include <unistd.h> #include <stdlib.h> #include <stdio.h> #include <string.h> #include <fcntl.h> #include <errno.h> #include <string> #include <stdexcept> #include <iostream> #include <sys/ioctl.h> #define SERVER_PORT 8888 #define BUFFER_LENGTH 1024 using namespace std; class SocketException : public std::logic_error { public: SocketException(const std::string& what) throw () : std::logic_error(what) {}; }; int SocketRead(int& fd, std::string& strValue) { // 每次只读取一个字节 int nRead = 1; auto_ptr<char> apBuf(new char[nRead]); int r = read(fd, apBuf.get(), nRead) ; if (0 < r) { strValue.assign(apBuf.get(), r); } return r; } int SocketWrite(int& fd, const char* pBuf, int nBufLen) { int nWrite = 0; int nError = -1; /* SIGPIPE：sent to a process when it attempts to write to a pipe without a process connected to the other end. The symbolic constant for SIGPIPE is defined in the header file signal.h. Symbolic signal names are used because signal numbers can vary across platforms. */ // SIG_IGN:忽略信号 sighandler_t sh = signal(SIGPIPE, SIG_IGN); while (nWrite < nBufLen) { nError = send(fd, pBuf + nWrite, nBufLen - nWrite, 0); if (0 > nError) { perror(strerror(errno)); // 见文末 if (nError == EINTR) continue; if (nError == EPIPE) { close(fd); } // 恢复信号 signal(SIGPIPE, sh); throw SocketException(string("SocketWrite error, ") + strerror(errno)); } else if (0 == nError) { signal(SIGPIPE, sh); throw SocketException(string("SocketWrite error, ") + strerror(errno)); } else { nWrite += nError; } } signal(SIGPIPE, sh); return nError; } void SetOption(int s, int level, int optname, const void *optval, socklen_t optlen) { if (setsockopt(s, level, optname, optval, optlen) < 0) { perror(strerror(errno)); } } int main(int argc, char*argv[]) { int fdServer = -1; int fdClient = -1; int nStatus = -1; pid_t pid = 0; int nSockAddrLen = sizeof(struct sockaddr_in); struct sockaddr_in addrServer; struct sockaddr_in addrSocket; bzero(&addrServer, sizeof(struct sockaddr_in)); bzero(&addrSocket, sizeof(struct sockaddr_in)); if(-1 == (fdServer = socket(AF_INET, SOCK_STREAM, 0))) { perror(strerror(errno)); exit(-1); } int nReuseAddr = 1; SetOption(fdServer, SOL_SOCKET, SO_REUSEADDR, &nReuseAddr, sizeof(int)); addrServer.sin_family = AF_INET; addrServer.sin_port = htons(SERVER_PORT); addrServer.sin_addr.s_addr = INADDR_ANY; if (-1 == bind(fdServer, (struct sockaddr *)&addrServer, sizeof(struct sockaddr))) { perror(strerror(errno)); exit(-1); } if (-1 == listen(fdServer, 128)) { perror(strerror(errno)); exit(-1); } while (true) { if ((fdClient = accept(fdServer, (struct sockaddr *)&addrSocket, (socklen_t*)&nSockAddrLen)) < 0) { perror(strerror(errno)); exit(-1); } printf("client address:%s\t port:%d\r\n", inet_ntoa(addrSocket.sin_addr), ntohs(addrSocket.sin_port)); if ((pid = fork()) < 0) { perror(strerror(errno)); exit(-1); } else if (0 == pid) /* clild */ { while (true) { try { std::string strValue; if(0 < SocketRead(fdClient, strValue)) { SocketWrite(fdClient, strValue.c_str(), strValue.length()); } else { close(fdClient); } // 要有延时，不然CPU使用率很高 usleep(10); } catch(const SocketException& e) { cerr << e.what() << endl; close(fdClient); break; } } } else /* parent */ { close(fdClient); } } return 0; }
-------------------------- select.cpp --------------------------
#include <sys/types.h> #include <sys/socket.h> #include <sys/un.h> #include <sys/time.h> #include <sys/ioctl.h> #include <netinet/in.h> #include <unistd.h> #include <stdlib.h> #include <iostream> #include <vector> #include <arpa/inet.h> #define SERVER_PORT 8888 #define NUM_MON 5 #define NUM_BUFFER 1024 #include <errno.h> using namespace std; void SetOption(int s, int level, int optname, const void *optval, socklen_t optlen) { if (setsockopt(s, level, optname, optval, optlen) < 0) { perror(strerror(errno)); } } int main(int argc, char*argv[]) { int fdServer = -1; int fdClient = -1; int fdMax = -1; int nRead = 0; char buf[NUM_BUFFER]; int nSockAddrLen = sizeof(struct sockaddr_in); struct sockaddr_in addrServer; struct sockaddr_in addrSocket; bzero(&addrServer, sizeof(struct sockaddr_in)); bzero(&addrSocket, sizeof(struct sockaddr_in)); int fdBuf[NUM_MON]; memset(fdBuf, -1, sizeof(fdBuf)); // 被监控的描述符集合 fd_set fsMon; // 事件的描述符集合 fd_set fsRead; FD_ZERO(&fsMon); FD_ZERO(&fsRead); if(-1 == (fdServer = socket(AF_INET, SOCK_STREAM, 0))) { perror(strerror(errno)); exit(-1); } int nReuseAddr = 1; SetOption(fdServer, SOL_SOCKET, SO_REUSEADDR, &nReuseAddr, sizeof(int)); addrServer.sin_family = AF_INET; addrServer.sin_port = htons(SERVER_PORT); addrServer.sin_addr.s_addr = INADDR_ANY; if (-1 == bind(fdServer, (struct sockaddr *)&addrServer, sizeof(struct sockaddr))) { perror(strerror(errno)); exit(-1); } if (-1 == listen(fdServer, 128)) { perror(strerror(errno)); exit(-1); } // 服务端是被监控对象之一 FD_SET(fdServer, &fsMon); fdMax = fdServer; while (true) { fsRead = fsMon; switch(select(fdMax + 1, &fsRead, NULL, NULL, NULL)) { case -1: perror(strerror(errno)); exit(-1); case 0: perror("timeout"); continue; default: break; } // 是否为fdServer的可读事件 if (FD_ISSET(fdServer, &fsRead)) { if (0 > (fdClient = accept(fdServer, (struct sockaddr *)&addrSocket, (socklen_t*)&nSockAddrLen))) { perror(strerror(errno)); exit(-1); } // socket加入fdBuf, fdBuf中是保存的所有socket的集合 for (int i = 0; i < NUM_MON; ++i) { if(-1 == fdBuf[i]) { fdBuf[i] = fdClient; break; } } // 把socket加入监控集合 FD_SET(fdClient, &fsMon) ; fdMax = max(fdMax, fdClient); continue; } for (int i = 0; i < NUM_MON; ++i) { if (-1 == fdBuf[i]) continue; if (!FD_ISSET(fdBuf[i], &fsMon)) continue; // 缓冲区中，是否有数据可读 ioctl(fdBuf[i], FIONREAD, &nRead); if (0 >= nRead) { // 非可读 FD_CLR(fdBuf[i], &fsMon); continue; } read(fdBuf[i], buf, nRead) ; write(fdBuf[i], buf, nRead) ; } } }
-------------------------- epoll.cpp --------------------------
#include <signal.h> #include <sys/types.h> #include <sys/socket.h> #include <sys/un.h> #include <sys/time.h> #include <sys/ioctl.h> #include <netinet/in.h> #include <sys/epoll.h> #include <unistd.h> #include <stdlib.h> #include <errno.h> #include <stdexcept> #include <fcntl.h> #include <iostream> using namespace std; #define SERVER_PORT 8888 class SocketException : public std::logic_error { public: SocketException(const std::string& what) throw () : std::logic_error(what) {}; }; int SocketRead(int& fd, std::string& strValue) { // 缓冲区中，是否有数据可读 int nRead = 0; ioctl(fd, FIONREAD, &nRead); if (nRead > 0) { auto_ptr<char> apBuf(new char[nRead]); read(fd, apBuf.get(), nRead) ; strValue.assign(apBuf.get(), nRead); } else { cout << nRead << endl; close(fd); } return nRead; } int SocketWrite(int& fd, const char* pBuf, int nBufLen) { // 参见fork.cpp int nWrite = 0; int nError = -1; sighandler_t sh = signal(SIGPIPE, SIG_IGN); while (nWrite < nBufLen) { nError = send(fd, pBuf + nWrite, nBufLen - nWrite, 0); if (0 > nError) { perror(strerror(errno)); if (nError == EINTR) continue; if (nError == EPIPE) { close(fd); } signal(SIGPIPE, sh); throw SocketException(string("SocketWrite error, ") + strerror(errno)); } else if (0 == nError) { // out pipe is closed signal(SIGPIPE, sh); throw SocketException(string("SocketWrite error, ") + strerror(errno)); } else { nWrite += nError; } } signal(SIGPIPE, sh); return nError; } void SetOption(int s, int level, int optname, const void *optval, socklen_t optlen) { if (setsockopt(s, level, optname, optval, optlen) < 0) { perror(strerror(errno)); } } // 设置socket为非阻塞式 void SetNonBlocking(int fd) { int flags = fcntl(fd, F_GETFL); flags |= O_NONBLOCK; fcntl(fd, F_SETFL, flags); } int main(int argc, char*argv[]) { int nfds, epfd, fdServer, fdClient; int maxevents = 1000; struct epoll_event ev, *events; epfd = epoll_create(128); int nSockAddrLen = sizeof(struct sockaddr_in); struct sockaddr_in addrServer; struct sockaddr_in addrSocket; bzero(&addrServer, sizeof(struct sockaddr_in)); bzero(&addrSocket, sizeof(struct sockaddr_in)); if(-1 == (fdServer = socket(AF_INET, SOCK_STREAM, 0))) { perror(strerror(errno)); exit(-1); } int nReuseAddr = 1; SetOption(fdServer, SOL_SOCKET, SO_REUSEADDR, &nReuseAddr, sizeof(int)); addrServer.sin_family = AF_INET; addrServer.sin_port = htons(SERVER_PORT); addrServer.sin_addr.s_addr = INADDR_ANY; if (-1 == bind(fdServer, (struct sockaddr *)&addrServer, sizeof(struct sockaddr))) { perror(strerror(errno)); exit(-1); } // 监控对象fdServer ev.data.fd = fdServer; // 事件：边沿触发，IN事件 ev.events = EPOLLIN | EPOLLET; if (epoll_ctl(epfd, EPOLL_CTL_ADD, fdServer, &ev) < 0) { perror(strerror(errno)); exit(-1); } if (-1 == listen(fdServer, 64)) { perror(strerror(errno)); exit(-1); } while(true) { nfds = epoll_wait(epfd, events, maxevents, -1); if (0 > nfds) { cerr << "epoll_wait:" << strerror(errno) << endl; } for(int n = 0; n < nfds; ++n) { // 事件主体为服务端？ if(events[n].data.fd == fdServer) { fdClient = accept(fdServer, (struct sockaddr *)&addrSocket, (socklen_t*)&nSockAddrLen); if(0 > fdClient) { perror(strerror(errno)); continue; } // 非阻塞式，咱们目标是，快点处理完来下一轮 SetNonBlocking(fdClient); // socket加入监控列表 ev.events = EPOLLIN | EPOLLET; ev.data.fd = fdClient; if (epoll_ctl(epfd, EPOLL_CTL_ADD, fdClient, &ev) < 0) { cerr << "epoll set insertion error: fd=" << fdClient << endl; return -1; } } else { int nError = 0; char buf[1024]; while(true) { nError = read(events[n].data.fd, buf, sizeof(buf)); cout << " read bytes:" << nError << endl; if (-1 == nError) { perror(strerror(errno)); // 这些见文末说明 if (nError == EINTR) continue; if (nError == EPIPE) { // 从监控列表中移除 epoll_ctl(epfd, EPOLL_CTL_DEL, events[n].data.fd, &ev); close(events[n].data.fd); break; } break; } else if (0 == nError) { // 从监控列表中移除 epoll_ctl(epfd, EPOLL_CTL_DEL, events[n].data.fd, &ev); close(events[n].data.fd); break; } SocketWrite(events[n].data.fd, buf, nError); } } } } return 0; }
---------------------- 文末 ------------------
EINTR、EPIPE、EAGAIN等参考 http://wenku.baidu.com/view/02a0cff34693daef5ef73d0f.html
