2021.12.28基于UDP同信的相关流程
作业
1、将TCP的CS模型再敲一遍
服务器
#include <myhead.h>
#define PORT 8888
#define IP "192.168.124.123"
int main(int argc, const char *argv[])
{//创建套接字//绑定本机IP和端口号//监听客户端请求//接收客户端连接请求//收发消息//创建套接字int oldfd ;if((oldfd = socket(AF_INET,SOCK_STREAM,0))==-1) //创建套接字{perror("socket");return -1;}//端口号快速复用int n = 2;if(setsockopt(oldfd,SOL_SOCKET,SO_REUSEADDR,&n,sizeof(n))==-1){perror("setsockopt");return -1;}//绑定本机IP和端口号struct sockaddr_in server = {.sin_family = AF_INET,.sin_port = htons(PORT),.sin_addr.s_addr = inet_addr(IP)};if(bind(oldfd,(struct sockaddr *)&server,sizeof(server))==-1){perror("bind");return -1;}//监听客户端连接请求，client变量接收客户端信息struct sockaddr_in client;int client_len = sizeof(client);int newfd;if(newfd = accept(oldfd,(struct sockaddr *)&client,&client_len)==-1){perror("accept");return -1;}printf("%s:%d连接\n",inet_ntoa(client.sin_addr),ntohs(client.sin_port));//收发消息char buff[1024];while(1){int res = recv(newfd,buff,sizeof(buff),0);if(res == 0){printf("客户端退出\n");break;}printf("收到消息：%s,收到消息的长度：%d\n",buff,res);strcat(buff,"霜雪");send(newfd,buff,sizeof(buff),0);bzero(buff,sizeof(buff));}close(newfd);close(oldfd);return 0;
}
客户端
#include <myhead.h>
#define IP "192.168.124.123"
#define SERPORT 9999
int main(int argc, const char *argv[])
{//1、创建套接字//2、绑定（不是必须绑定）//3、连接//4、收发消息int oldfd = socket(AF_INET,SOCK_STREAM,0);if(oldfd==-1){perror("socket");return -1;}
#if 0//绑定固定的IP和端口号(不是必须的)struct sockaddr_in client = {.sin_family =AF_INET,.sin_port = htons(7899),//自定义端口号.sin_addr.s_addr = inet_addr("192.168.124.34")};if(bind(oldfd,(struct sockaddr *)&client,sizeof(client))==-1){perror("bind");return -1;}
#endif//连接服务器struct sockaddr_in server = {.sin_family =AF_INET,.sin_port = htons(SERPORT),//注意端口号需要服务器端口.sin_addr.s_addr = inet_addr(IP)};if(connect(oldfd,(struct sockaddr *)&server,sizeof(server))==-1){perror("connect");return -1;}//收发消息char buff[1024];while(1){fgets(buff,sizeof(buff),stdin);buff[strlen(buff)-1] = '\0';send(oldfd,buff,sizeof(buff),0);if(strcmp(buff,"quit")==0)//退出客户端{break;}bzero(buff,sizeof(buff));recv(oldfd,buff,sizeof(buff),0);//阻塞接收服务器消息printf("服务器发来消息：%s\n",buff);}close(oldfd);return 0;
}2、UDP服务器中，使用connect函数，实现唯一的客户端与服务器通话。
服务器
#include <myhead.h>
#define PORT 8888#define IP "192.168.124.123"int main(int argc, const char *argv[])
{//创建套接字int oldfd = socket(AF_INET,SOCK_DGRAM,0);if(oldfd == -1){perror("socket");return -1;}//绑定struct sockaddr_in server = {.sin_family = AF_INET,.sin_port = htons(PORT),.sin_addr.s_addr = inet_addr(IP)};if(bind (oldfd,(struct sockaddr *)&server,sizeof(server))==-1){perror("bind");return -1;}struct sockaddr_in client;int client_len = sizeof(client);char buff[1024];int flag = 0;while(1){recvfrom(oldfd,buff,sizeof(buff),0,(struct sockaddr *)&client,&client_len);printf("%s:%d信息：%s\n",inet_ntoa(client.sin_addr),ntohs(client.sin_port),buff);if(connect(oldfd,(struct sockaddr *)&client,sizeof(client))==-1){perror("connect");return -1;}while(1){int res = recvfrom(oldfd,buff,sizeof(buff),0,NULL,NULL);printf("%s\n",buff);strcat(buff,"周日还要上课，吴！！！！");sendto(oldfd,buff,sizeof(buff),0,NULL,0);bzero(buff,sizeof(buff));if(res == 0){printf("退出客户端\n");break;}}}return 0;
}
客户端
#include <myhead.h>
#define IP "192.168.124.123"
#define PORT 8888
int main(int argc, const char *argv[])
{//1、创建套接字int oldfd = socket(AF_INET,SOCK_DGRAM,0);if(oldfd==-1){perror("socket");return -1;}//2、收发消息struct sockaddr_in server = {.sin_family = AF_INET,.sin_port = htons(PORT),.sin_addr.s_addr = inet_addr(IP)};if(connect(oldfd,(struct sockaddr *)&server,sizeof(server))==-1){perror("connect");return -1;} char buff[1024];while(1){fgets(buff,sizeof(buff),stdin);buff[strlen(buff)-1] = '\0';sendto(oldfd,buff,sizeof(buff),0,(struct sockaddr *)&server,sizeof(server));bzero(buff,sizeof(buff));recvfrom(oldfd,buff,sizeof(buff),0,NULL,NULL);printf("接收服务器信息：%s\n",buff);}return 0;
}
笔记整理
流程图
UDP服务器
1、创建套接字。
2、绑定本机IP和端口号。
3、收发消息，由于不知道对方是谁，对方也不知道您是谁，所以在发送时附带自己的信息，接收时接收对方信息。
UDP相关API
#include <sys/types.h>
#include <sys/socket.h>
ssize_t sendto(int sockfd, const void *buf, size_t len, int flags, const struct sockaddr *dest_addr, socklen_t addrlen);
功能：发送信息函数
参数1：套接字
参数2：发送的信息
参数3：信息大小
参数4： 0：阻塞接收
MSG_DONTWAIT:费阻塞接收
参数5：填写发送目标的IP和端口号 参数6：参数5的大小。
返回值：成功返回发送的字节个数，失败返回-1，并置位错误码。
#include <sys/types.h>
#include <sys/socket.h>
ssize_t recvfrom(int sockfd, void *buf, size_t len, int flags, struct sockaddr *src_addr, socklen_t *addrlen);
功能：接收信息函数
参数1：套接字
参数2：发送的信息
参数3：信息大小
参数4： 0：阻塞接收
MSG_DONTWAIT:费阻塞接收
参数5：自动填充发信息的主机信息。
返回值：成功返回发送的字节个数，失败返回-1，并置位错误码。
、UDP服务器
#include <myhead.h>
#define PORT 8888
#define IP "192.168.124.34"int main(int argc, const char *argv[])
{//1、创建UDP套接字int oldfd = socket(AF_INET,SOCK_DGRAM,0);if(oldfd==-1){perror("socket");return -1;}//2、绑定struct sockaddr_in server = {.sin_family = AF_INET,.sin_port = htons(PORT),.sin_addr .s_addr = inet_addr(IP)};if(bind(oldfd,(struct sockaddr *)&server,sizeof(server))==-1){perror("bind");return -1;}//收发消息struct sockaddr_in client;int client_len = sizeof(client);char buff[1024];while(1){//接收客户端消息时会将客户端信息写入clientrecvfrom(oldfd,buff,sizeof(buff),0,(struct sockaddr *)&client,&client_len);printf("收到%s：%d的消息：%s\n",inet_ntoa(client.sin_addr),ntohs(client.sin_port),buff);strcat(buff,"元旦不放假难受");sendto(oldfd,buff,sizeof(buff),0,(struct sockaddr *)&client,sizeof(client));//收到谁的信息就发给谁}return 0;
}4、UDP客户端
1、创建套接字
2、收发消息
#include <myhead.h>
#define IP "192.168.124.34"
#define PORT 8888
int main(int argc, const char *argv[])
{//1、创建套接字int oldfd = socket(AF_INET,SOCK_DGRAM,0);if(oldfd==-1){perror("socket");return -1;}//2、收发消息struct sockaddr_in server = {.sin_family = AF_INET,.sin_port = htons(PORT),.sin_addr.s_addr = inet_addr(IP)};char buff[1024];while(1){fgets(buff,sizeof(buff),stdin);buff[strlen(buff)-1] = '\0';sendto(oldfd,buff,sizeof(buff),0,(struct sockaddr *)&server,sizeof(server));bzero(buff,sizeof(buff));recvfrom(oldfd,buff,sizeof(buff),0,NULL,NULL);printf("接收服务器信息：%s\n",buff);}return 0;
}思维导图
