linux系统和网络(四):网络

本文主要探讨linux网络相关知识,详细介绍看本博客其他博文。

网络基础(参考本博客其他文章：基础网络知识，socket网络编程，基于socket的聊天室和简易ftp)
        路由器是局域网和外部网络通信出入口
        DNS实现域名和IP地址之间转换
        NAT是局域网主机发送数据包给外网将主机内网IP转换为外网IP
        网段 = IP地址 & 子网掩码

demo:

编写client和server,server用于存储个人信息，client下发个人信息增删改查等信息到server,server执行并反馈结果

server

#include <stdio.h>
#include <sys/socket.h>
#include <sys/types.h>          
#include <sys/socket.h>
#include <arpa/inet.h>
#include <string.h>
#include <stdlib.h>#define SERPORT         8001
#define SERADDR         "192.168.200.181"
#define BACKLOG         100#define CMD_REGISTER            1
#define CMD_CHECK               2
#define CMD_GETINFO             3
#define CMD_DELETE              4typedef struct people_info
{char name[20];int age;int cmd;char result[20];
} info;typedef struct mark_flag
{int flg;int zero;
} mark;char name[3][10] = {0};
int age[3] = {0};
int cli_fd;
info st;
mark flag;void have_connect()
{struct sockaddr_in ser_addr = {0};struct sockaddr_in cli_addr = {0};socklen_t len = sizeof(cli_addr);int sockfd = socket(AF_INET,SOCK_STREAM,0);if(sockfd == -1){perror("socket");exit(-1);}ser_addr.sin_family = AF_INET;ser_addr.sin_port = htons(SERPORT);ser_addr.sin_addr.s_addr = inet_addr(SERADDR);bind(sockfd, (const struct sockaddr *)&ser_addr, sizeof(ser_addr));listen(sockfd, BACKLOG);cli_fd = accept(sockfd, (struct sockaddr *)&cli_addr,&len);send(cli_fd,"connect sucess",strlen("connect sucess"),0);printf("%s connect ...\n",inet_ntoa(cli_addr.sin_addr));}void find_info()
{int i;for(i = 0;i < (sizeof(age)/sizeof(age[0]));i++){if(!strncmp(name[i],st.name,strlen(st.name)))flag.flg = i;if(age[i] == 0)flag.zero = i;}
}void register_info()
{find_info();if(flag.flg != -1){strcpy(st.result,"user existed");}if(flag.zero == -1 &&  flag.flg == -1){strcpy(st.result,"user full");}if(flag.zero != -1 && flag.flg == -1){strcpy(name[flag.zero],st.name);age[flag.zero]  = st.age;strcpy(st.result,"register ok");}}void get_info()
{find_info();if(flag.flg == -1){strcpy(st.result,"have no user");}else{st.age = age[flag.flg];strcpy(st.name,name[flag.flg]);}
}void check_info()
{find_info();if(flag.flg == -1){strcpy(st.result,"have no user");}else{strcpy(st.result,"user existed");}
}void delete_info()
{find_info();if(flag.flg == -1){strcpy(st.result,"have no user");}else{age[flag.flg] = 0;memset(name[flag.flg],0,sizeof(name[flag.flg]));strcpy(st.result,"user deleted");}
}int main()
{have_connect();while(1){memset(&st,0,sizeof(st));recv(cli_fd, &st, sizeof(info), 0);memset(st.result,0,sizeof(st.result));flag.flg = -1;flag.zero = -1;if(st.cmd == CMD_REGISTER){register_info();}if(st.cmd == CMD_GETINFO){get_info();}if(st.cmd == CMD_CHECK){check_info();}if(st.cmd == CMD_DELETE){delete_info();}send(cli_fd,&st,sizeof(st),0);}return 0;
}

client

#include <stdio.h>
#include <sys/socket.h>
#include <sys/types.h>          
#include <sys/socket.h>
#include <arpa/inet.h>
#include <string.h>
#include <stdlib.h>#define SERPORT         8001
#define SERADDR         "192.168.200.181"#define CMD_REGISTER            1
#define CMD_CHECK               2
#define CMD_GETINFO             3
#define CMD_DELETE              4typedef struct people_info
{char name[20];int age;int cmd;char result[20];
} info;int sockfd;
info st;void have_connect()
{struct sockaddr_in ser_addr = {0};char buf[20] = {0};sockfd = socket(AF_INET,SOCK_STREAM,0);if(sockfd == -1){perror("socket");exit(-1);}ser_addr.sin_family = AF_INET;ser_addr.sin_port = htons(SERPORT);ser_addr.sin_addr.s_addr = inet_addr(SERADDR);bind(sockfd, (const struct sockaddr *)&ser_addr, sizeof(ser_addr));connect(sockfd, (const struct sockaddr *)&ser_addr, sizeof(ser_addr));recv(sockfd,buf, sizeof(buf), 0);printf("%s\n",buf);
}int main()
{int flag;have_connect();while(1){memset(&st,0,sizeof(st));printf("ex:1 : register 2 : check 3 : get 4 : delete,please input:");scanf("%d",&flag);if(flag ==1){printf("name:");scanf("%s",st.name);printf("age:");scanf("%d",&st.age);st.cmd = CMD_REGISTER;}else{printf("name:");scanf("%s",st.name);if(flag ==2)st.cmd = CMD_CHECK;if(flag ==3)st.cmd = CMD_GETINFO;if(flag ==4)st.cmd = CMD_DELETE;if(flag == 0 || flag > 4)printf("input error\n");}send(sockfd,&st,sizeof(st),0);recv(sockfd,&st, sizeof(st), 0);if(strlen(st.result)){printf("%s\n",st.result);}else{printf("name : %s, age : %d\n",st.name,st.age);}}
}

结果显示：