1多进程并发服务器
使用多进程并发服务器时要考虑以下几点：
A.父最大文件描述个数（父进程中需要close关闭accept返回的新文件描述符）
B.系统内创建进程个数（和内存大小相关）
C.进程创建过多是否降低整体服务性能（进程调度）
2.案例说明
server.c,代码如下：
| #include <stdio.h> #include <string.h> #include <netinet/in.h> #include <arpa/inet.h> #include <signal.h> #include <sys/wait.h> #include <sys/types.h> #include <arpa/inet.h> #include <ctype.h> #include <unistd.h> #include "wrap.h"
#define MAXLINE 80 #define SERV_PORT 8000
void do_sigchild(int num) { waitpid(0,NULL,WNOHANG); }
int main(void) { struct sockaddr_in servaddr,cliaddr; socklen_t cliaddr_len; int listenfd,connfd; char buf[MAXLINE]; //INET_ADDRSTRLEN是ip地址的最大长度，是系统定义的一个宏 char str[INET_ADDRSTRLEN]; int i,n; pid_t pid;
struct sigaction newact; newact.sa_handler = do_sigchild; sigemptyset(&newact.sa_mask); newact.sa_flags = 0; //发信号 sigaction(SIGCHLD,&newact,NULL);
//1.这里建立一个TCP的连接，因为是SOCK_STREAM的，表示的是TCP的 listenfd = Socket(AF_INET,SOCK_STREAM,0); //将seraddr内容清零 bzero(&servaddr,sizeof(servaddr)); servaddr.sin_family = AF_INET; servaddr.sin_addr.s_addr = htonl(INADDR_ANY); servaddr.sin_port = htons(SERV_PORT); //2.绑定ip地址和端口号 Bind(listenfd,(struct sockaddr *)&servaddr,sizeof(servaddr)); //监听，最多的可以是20个 Listen(listenfd,20);
printf("Accepting connections...\n"); while(1) { cliaddr_len = sizeof(cliaddr_len); //connfd:这里才是后续进程需要用的文件描述符 //listenfd:已经不用里，可以被销毁,这个程序是在子进程里面销毁 connfd = Accept(listenfd,(struct sockaddr *)&cliaddr,&cliaddr_len);
pid = fork(); if(pid ==0) { if(pid == 0) { Close(listenfd); while(1) { n = Read(connfd,buf,MAXLINE); if(n == 0) { printf("the other side has been closed.\n"); break; } printf("received from %s at PORT %d\n", inet_ntop(AF_INET,&cliaddr.sin_addr.s_addr,str,sizeof(str)), ntohs(cliaddr.sin_port));
for(i = 0; i< n; i++) { buf[i] = toupper(buf[i]); } Write(connfd,buf,n); } Close(connfd); return 0; } else if(pid > 0) { Close(connfd); } else { perr_exit("fork"); } } } } |
client.c
| #include <stdio.h> #include <string.h> #include <unistd.h> #include <netinet/in.h> #include <arpa/inet.h> #include "wrap.h"
#define MAXLINE 80 #define SERV_PORT 8000
int main(int argc,char *argv[]) { struct sockaddr_in servaddr; char buf[MAXLINE]; int sockfd,n;
sockfd = Socket(AF_INET,SOCK_STREAM,0);
bzero(&servaddr,sizeof(servaddr)); servaddr.sin_family = AF_INET; inet_pton(AF_INET,"127.0.0.1",&servaddr.sin_addr.s_addr); servaddr.sin_port = htons(SERV_PORT);
Connect(sockfd,(struct sockaddr *)&servaddr,sizeof(servaddr));
while(fgets(buf,MAXLINE,stdin) != NULL) { Write(sockfd,buf,strlen(buf)); n = Read(sockfd,buf,MAXLINE); if(n == 0) { printf("the other side has ben closed.\n"); } else { Write(STDOUT_FILENO,buf,n); } }
Close(sockfd); return 0; } |
wrap.h
| #ifndef __WRAP_H_ #define __WRAP_H_
void perr_exit(const char *s); int Accept(int fd, struct sockaddr *sa, socklen_t *salenptr); void Bind(int fd, const struct sockaddr *sa, socklen_t salen); void Connect(int fd, const struct sockaddr *sa, socklen_t salen); void Listen(int fd, int backlog); int Socket(int family, int type, int protocol); ssize_t Read(int fd, void *ptr, size_t nbytes); ssize_t Write(int fd, const void *ptr, size_t nbytes); void Close(int fd); ssize_t Readn(int fd, void *vptr, size_t n); ssize_t Writen(int fd, const void *vptr, size_t n); static ssize_t my_read(int fd, char *ptr); ssize_t Readline(int fd, void *vptr, size_t maxlen);
#endif |
wrap.c
| #include <stdlib.h> #include <errno.h> #include <sys/socket.h>
void perr_exit(const char *s) { perror(s); exit(1); }
int Accept(int fd, struct sockaddr *sa, socklen_t *salenptr) { int n;
again: if ( (n = accept(fd, sa, salenptr)) < 0) { if ((errno == ECONNABORTED) || (errno == EINTR)) goto again; else perr_exit("accept error"); } return n; }
void Bind(int fd, const struct sockaddr *sa, socklen_t salen) { if (bind(fd, sa, salen) < 0) perr_exit("bind error"); }
void Connect(int fd, const struct sockaddr *sa, socklen_t salen) { if (connect(fd, sa, salen) < 0) perr_exit("connect error"); }
void Listen(int fd, int backlog) { if (listen(fd, backlog) < 0) perr_exit("listen error"); }
int Socket(int family, int type, int protocol) { int n;
if ( (n = socket(family, type, protocol)) < 0) perr_exit("socket error"); return n; }
ssize_t Read(int fd, void *ptr, size_t nbytes) { ssize_t n;
again: if ( (n = read(fd, ptr, nbytes)) == -1) { if (errno == EINTR) goto again; else return -1; } return n; }
ssize_t Write(int fd, const void *ptr, size_t nbytes) { ssize_t n;
again: if ( (n = write(fd, ptr, nbytes)) == -1) { if (errno == EINTR) goto again; else return -1; } return n; }
void Close(int fd) { if (close(fd) == -1) perr_exit("close error"); } ssize_t Readn(int fd, void *vptr, size_t n) { size_t nleft; ssize_t nread; char *ptr;
ptr = vptr; nleft = n; while (nleft > 0) { if ( (nread = read(fd, ptr, nleft)) < 0) { if (errno == EINTR) nread = 0; else return -1; } else if (nread == 0) break;
nleft -= nread; ptr += nread; } return n - nleft; }
ssize_t Writen(int fd, const void *vptr, size_t n) { size_t nleft; ssize_t nwritten; const char *ptr;
ptr = vptr; nleft = n; while (nleft > 0) { if ( (nwritten = write(fd, ptr, nleft)) <= 0) { if (nwritten < 0 && errno == EINTR) nwritten = 0; else return -1; }
nleft -= nwritten; ptr += nwritten; } return n; } static ssize_t my_read(int fd, char *ptr) { static int read_cnt; static char *read_ptr; static char read_buf[100];
if (read_cnt <= 0) { again: if ( (read_cnt = read(fd, read_buf, sizeof(read_buf))) < 0) { if (errno == EINTR) goto again; return -1; } else if (read_cnt == 0) return 0; read_ptr = read_buf; } read_cnt--; *ptr = *read_ptr++; return 1; }
ssize_t Readline(int fd, void *vptr, size_t maxlen) { ssize_t n, rc; char c, *ptr;
ptr = vptr; for (n = 1; n < maxlen; n++) { if ( (rc = my_read(fd, &c)) == 1) { *ptr++ = c; if (c == '\n') break; } else if (rc == 0) { *ptr = 0; return n - 1; } else { return -1; } } *ptr = 0; return n; } |
运行结果（编译server）：
运行client端
