简单的UDP回射程序

Server：

#include <stdio.h>
#include <string.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <sys/socket.h>
#define MAXSIZE 1024
#define SERV_PORT 2000
void dg_echo(int sockfd, struct sockaddr * pcliaddr, socklen_t clilen)
{
    int n;
    socklen_t len;
    while(1)
    {
        char mesg[MAXSIZE];
        //回射机制
        len=clilen;
        n=recvfrom(sockfd,mesg,MAXSIZE,0,pcliaddr,&len);
        char servermsg[MAXSIZE]="From Server: ";
        int l = strlen(servermsg);
        servermsg[l]='\0';
        strcat(servermsg,mesg);
        sendto(sockfd,servermsg,n+l,0,pcliaddr,len);
    }
}
int main( int args, char ** argv)
{
    int sockfd;
    struct sockaddr_in serveraddr, clientaddr;
    sockfd=socket(AF_INET,SOCK_DGRAM,0);
    bzero(&serveraddr,sizeof(serveraddr));
    serveraddr.sin_family=AF_INET;
    serveraddr.sin_addr.s_addr=htonl(INADDR_ANY);
    serveraddr.sin_port=htons(SERV_PORT);
    bind(sockfd,(struct sockaddr *)&serveraddr,sizeof(serveraddr));
    dg_echo(sockfd,(struct sockaddr *)&serveraddr,sizeof(clientaddr));
    return 0;
}

Client：

#include <stdio.h>
#include <string.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <sys/socket.h>
#define MAXSIZE  1024
#define SERVER_PORT 2000
void dg_client (FILE* fp,int sockfd, const struct sockaddr * pservaddr,socklen_t serverlen)
{
    int n;
    char sendline[MAXSIZE],recvline[MAXSIZE+1];
    printf("From Client: ");
    while(fgets(sendline,MAXSIZE,fp)!=NULL)
    {
        sendto(sockfd,sendline,strlen(sendline),0,pservaddr,serverlen);
        n=recvfrom(sockfd,recvline,MAXSIZE,0,NULL,NULL);
        recvline[n]='\0';
        fputs(recvline,stdout);
        printf("From Client: ");
    }
}
int main (int args, char ** argv )
{
    int sockfd;
    struct sockaddr_in serveraddr;
    bzero(&serveraddr,sizeof(serveraddr));
    
    serveraddr.sin_family=AF_INET;
    serveraddr.sin_port=htons(SERVER_PORT);
    inet_pton(AF_INET,"10.3.1.215",&serveraddr.sin_addr);
    sockfd=socket(AF_INET,SOCK_DGRAM,0);
    dg_client(stdin,sockfd,(struct sockaddr * )&serveraddr,sizeof(serveraddr));
    return 0;
        
}