本博客参考《Linux C/C++服务器开发实践》—— 朱文伟 李建英
什么是循环服务器?
循环服务器在同一个时刻只能响应一个客户端的请求,处理完一个客户端的工作后,才能处理下一个客户端的工作,就好像分时工作一样。循环服务器指的是对于客户端的请求和连接,服务器在处理完毕一个后,再处理另一个,即串行处理客户机的请求。这个I/O模型对应的是同步阻塞模型。
有关五种网络I/O模型的详细了解,请参考下面的博客:
链接:Linux网络编程之I/O模型(详解)
UDP循环服务器
UDP循环服务器的实现方法:UDP服务器每次从套接字上读取一个客户端的请求并处理,然后将处理结果返回给客户端。伪代码如下:
socket();
bind();
while(1){recvfrom();process();sendto();
}
因为UDP是无连接的,没有一个客户端可以一直占用服务器,服务器能满足每一个客户端的请求。
一个简单的UDP循环服务器代码
udpserver.cpp
#include "myhead.h"#define PORT 10024
char rbuf[50], sbuf[100];int main(){int sockfd, size, ret, val;char on = 1;struct sockaddr_in saddr;struct sockaddr_in raddr;//设置地址信息,IP信息size = sizeof(struct sockaddr_in);val = sizeof(struct sockaddr);memset(&saddr, 0, size);saddr.sin_family = AF_INET;saddr.sin_port = htons(PORT);saddr.sin_addr.s_addr = htonl(INADDR_ANY);//创建UDP套接字sockfd = socket(AF_INET, SOCK_DGRAM, 0);if(sockfd < 0){perror("create sockfd fail\n");return -1;}//设置端口复用setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));//绑定地址信息ret = bind(sockfd, (struct sockaddr*)&saddr, val);if(ret < 0){perror("bind fail\n");return -1;}while(1){puts("waitting data\n");ret = recvfrom(sockfd, rbuf, sizeof(rbuf), 0, (struct sockaddr*)&raddr, (socklen_t*)&val);if(ret < 0){perror("recvfrom failed\n");}printf("recv data:%s\n", rbuf);snprintf(sbuf, sizeof(sbuf), "server has received your data(%s)\n", rbuf);ret = sendto(sockfd, sbuf, sizeof(rbuf), 0, (struct sockaddr*)&raddr,val);memset(rbuf, 0, sizeof(rbuf));}close(sockfd);getchar();return 0;
}
udpclient.cpp
#include <stdio.h>
#include <winsock.h>
#pragma comment(lib, "wsock32")
#define BUF_SIZE 200
#define PORT 10024
#define IP "192.168.159.128"
char wbuf[50], rbuf[100];int main()
{SOCKET s;int len = -1;WSADATA wsadata;struct hostent* phe;struct servent* pse;struct protoent* ppe;struct sockaddr_in saddr, raddr;int fromlen, ret, type;if (WSAStartup(MAKEWORD(2, 0), &wsadata) != 0) {printf("WSAStarup failed\n");return -1;}memset(&saddr, 0, sizeof(saddr));saddr.sin_family = AF_INET;saddr.sin_port = htons(PORT);saddr.sin_addr.s_addr = inet_addr(IP);if ((ppe = getprotobyname("UDP")) == 0) {printf("get protocol information error \n");WSACleanup();return -1;}s = socket(PF_INET, SOCK_DGRAM, ppe->p_proto);if (s == INVALID_SOCKET) {printf(" create socket error \n");WSACleanup();return -1;}fromlen = sizeof(struct sockaddr);printf("please inter data:");scanf_s("%s", wbuf, sizeof(wbuf));ret = sendto(s, wbuf, sizeof(wbuf), 0, (struct sockaddr*)&saddr, sizeof(struct sockaddr));if (ret < 0) {perror("sendto failed\n");}len = recvfrom(s, rbuf, sizeof(rbuf), 0, (struct sockaddr*)&raddr, &fromlen);if (len < 0) perror("recvfrom fail\n");printf("server reply:%s\n", rbuf);closesocket(s);WSACleanup();return 0;
}
注意,为了更贴近一线企业实战环境,客户端的程序是放到Windows上运行的,所以它的代码也使用了Windows系统提供的接口。该代码可以在Visual C++上运行,如果想深入了解Visual C++,可以参考清华大学出版社的《Viusal C++ 2017从入门到精通》一书。
TCP循环服务器
TCP服务器接受一个客户端的连接,然后处理,完成了这个客户端的所有请求后,断开连接。伪代码如下:
socket();
bind();
listen();
while(1){accept();process();close();
}
注:TCP循环服务器一次只能处理一个客户端的请求(除非使用一客户端一线程)。只有在这个客户端的所有请求都满足后,服务器才可以继续后面的请求。如果一个客户端占住服务器不放,则其他的客户端都不能工作,因此TCP服务器一般很少使用这个模型。
链接: 想了解更多服务器模型,可以参考这里
一个简单的TCP循环服务器代码
tcpserver.cpp
#include "myhead.h"
#define BUF_SIZE 200
#define PORT 8888int main()
{struct sockaddr_in fsin;int clisock,alen, connum = 0, len, s;char buf[BUF_SIZE] = "hi,client", rbuf[BUF_SIZE];struct servent *pse; /* server information */struct protoent *ppe; /* proto information */struct sockaddr_in sin; /* endpoint IP address */memset(&sin, 0, sizeof(sin));sin.sin_family = AF_INET;sin.sin_addr.s_addr = INADDR_ANY;sin.sin_port = htons(PORT);s = socket(PF_INET, SOCK_STREAM, 0);if (s == -1){printf("creat socket error \n");getchar();return -1;}if (bind(s, (struct sockaddr *)&sin, sizeof(sin)) == -1){printf("socket bind error \n");getchar();return -1;}if (listen(s, 10) == -1){printf(" socket listen error \n");getchar();return -1;}while (1){alen = sizeof(struct sockaddr);puts("waiting client...");clisock = accept(s, (struct sockaddr *)&fsin,(socklen_t*)&alen);if (clisock == -1){printf("accept failed\n");getchar();return -1;}connum++;printf("%d client comes\n", connum);len = recv(clisock, rbuf, sizeof(rbuf), 0);if (len < 0) perror("recv failed");sprintf(buf,"Server has received your data(%s).", rbuf);send(clisock, buf, strlen(buf), 0);close(clisock);}return 0;
}
tcpclient.cpp
#include "myhead.h"
#define BUF_SIZE 200
#define PORT 8888
char wbuf[50], rbuf[100];
int main()
{char buff[BUF_SIZE];SOCKET s;int len;WSADATA wsadata;struct hostent *phe; /*host information */struct servent *pse; /* server information */struct protoent *ppe; /*protocol information */struct sockaddr_in saddr; /*endpoint IP address */int type;if (WSAStartup(MAKEWORD(2, 0), &wsadata) != 0){printf("WSAStartup failed\n");WSACleanup();return -1;}memset(&saddr, 0, sizeof(saddr));saddr.sin_family = AF_INET;saddr.sin_port = htons(PORT);saddr.sin_addr.s_addr = inet_addr("192.168.0.153");s = socket(PF_INET, SOCK_STREAM, 0);if (s == INVALID_SOCKET){printf(" creat socket error \n");WSACleanup();return -1;}if (connect(s, (struct sockaddr *)&saddr, sizeof(saddr)) == SOCKET_ERROR){printf("connect socket error \n");WSACleanup();return -1;}printf("please enter data:");scanf_s("%s", wbuf, sizeof(wbuf));len = send(s, wbuf, sizeof(wbuf), 0);if (len < 0) perror("send failed");len = recv(s, rbuf, sizeof(rbuf), 0);if (len < 0) perror("recv failed");printf("server reply:%s\n", rbuf);closesocket(s);WSACleanup();return 0;
}
都读到这了,免费给个三连支持一下吧,下一期我会继续努力~
附录(myhead.h)
// myhead.h
#ifndef _MYHEAD_H
#define _MYHEAD_H
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <sys/mman.h>
#include <linux/input.h> //跟输入子系统模型有关的头文件
#include <dirent.h>
#include <stdbool.h>
#include <strings.h>
#include <sys/wait.h>
#include <signal.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <sys/msg.h>
#include <sys/sem.h>
#include <pthread.h>
#include <semaphore.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <net/if.h>
#include <netdb.h>
#include <poll.h>
#include <sys/epoll.h>
#endif