1多线程并发服务器
在使用线程模型开发服务器时需要考虑以下问题：
A调整进程最大文件描述符上限
B线程如有共享数据，考虑线程同步
C服务于客户端线程退出时，退出处理。（退出值，分离态）
D系统负载，随着连接客户端增加，导致其它线程不能及时得到CPU
2.案例说明
server.c,代码如下：
| /* server.c */ #include <stdio.h> #include <string.h> #include <netinet/in.h> #include <arpa/inet.h> #include <pthread.h> #include "wrap.h" #define MAXLINE 80 #define SERV_PORT 8000
struct s_info { struct sockaddr_in cliaddr; int connfd; };
void *do_work(void *arg) { int n,i; struct s_info *ts = (struct s_info*)arg; char buf[MAXLINE]; char str[INET_ADDRSTRLEN]; /*可以在创建线程前设置线程创建属性,设为分离态,哪种效率高内？ 答：线程前设置线程属性*/ pthread_detach(pthread_self()); while (1) { n = Read(ts->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, &(*ts).cliaddr.sin_addr, str, sizeof(str)), ntohs((*ts).cliaddr.sin_port)); for (i = 0; i < n; i++) { buf[i] = toupper(buf[i]); } Write(ts->connfd, buf, n); } Close(ts->connfd); }
int main(void) { struct sockaddr_in servaddr, cliaddr; socklen_t cliaddr_len; int listenfd, connfd; int i = 0; pthread_t tid; struct s_info ts[383]; listenfd = Socket(AF_INET, SOCK_STREAM, 0); bzero(&servaddr, sizeof(servaddr)); servaddr.sin_family = AF_INET; servaddr.sin_addr.s_addr = htonl(INADDR_ANY); servaddr.sin_port = htons(SERV_PORT); Bind(listenfd, (struct sockaddr *)&servaddr, sizeof(servaddr)); Listen(listenfd, 20); printf("Accepting connections ...\n"); while (1) { cliaddr_len = sizeof(cliaddr); connfd = Accept(listenfd, (struct sockaddr *)&cliaddr, &cliaddr_len); ts[i].cliaddr = cliaddr; ts[i].connfd = connfd; /*达到线程最大数时，pthread_create出错处理,增加服务器稳定性*/ pthread_create(&tid, NULL, do_work, (void*)&ts[i]); i++; } Close(listenfd); return 0; } |
client.c
| /* client.c */ #include <stdio.h> #include <string.h> #include <unistd.h> #include <netinet/in.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); 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 been 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; } |
