linux学习之多高并发服务器篇（一）
高并发服务器
高并发服务器
并发服务器开发
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：
- 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)
- 系统内创建进程个数(内存大小相关)
- 进程创建过多是否降低整体服务性能(进程调度)
server
/* server.c */
#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 "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];
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;
sigaction(SIGCHLD, &newact, NULL);
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 ...
");
while (1) {
cliaddr_len = sizeof(cliaddr);
connfd = Accept(listenfd, (struct sockaddr *)&cliaddr, &cliaddr_len);
//多进程服务器
pid = fork();
if (pid == 0) {
//子进程
Close(listenfd);
while (1) {//可以循环读
n = Read(connfd, buf, MAXLINE);
if (n == 0) {
printf("the other side has been closed.
");
break;
}
printf("received from %s at PORT %d
",
inet_ntop(AF_INET, &cliaddr.sin_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);//若不关长期以往会导致文见文件描述符关闭
return 0;
}
else if (pid > 0) {
Close(connfd);
}
else
perr_exit("fork");
}
}
client
#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.
");
else
Write(STDOUT_FILENO, buf, n);
}
Close(sockfd);
return 0;
}
2.多线程并发服务器 在使用线程模型开发服务器时需考虑以下问题：
- 调整进程内最大文件描述符上限
- 线程如有共享数据，考虑线程同步
- 服务于客户端线程退出时，退出处理。（退出值，分离态）
- 系统负载，随着链接客户端增加，导致其它线程不能及时得到CPU
多线程
server
/* 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？ */
pthread_detach(pthread_self());
while (1) {
n = Read(ts->connfd, buf, MAXLINE);
if (n == 0) {
printf("the other side has been closed.
");
break;
}
printf("received from %s at PORT %d
",
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 ...
");
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++;
}
return 0;
}
client
/* 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.
");
else
Write(STDOUT_FILENO, buf, n);
}
Close(sockfd);
return 0;
}