网络编程udp入门

老师布置的作业

echo4_server.c

 #include<stdio.h>
 #include<stdlib.h>
 #include<string.h>
 #include<unistd.h>
 #include<arpa/inet.h>
 #include<sys/socket.h>

 #define BUF_SIZE 10 //一次最大传输大小
 void error_handling(char *message); //异常

 int main(int argc,char** argv)
 {
     int serv_sock,n;
     char message[BUF_SIZE*+],message1[BUF_SIZE+];
     int str_len;
     socklen_t clnt_adr_sz;
     struct sockaddr_in serv_adr,clnt_adr;
     if(argc!=){
         printf("Usage : %s <port>\n",argv[]);
         exit();
     }
     serv_sock=socket(PF_INET,SOCK_DGRAM,);
     if(serv_sock == -){
         error_handling("UDP socket creattion error");
     }

     memset(&serv_adr,,sizeof(serv_adr));
     serv_adr.sin_family=AF_INET;
     serv_adr.sin_addr.s_addr=htonl(INADDR_ANY);
     serv_adr.sin_port=htons(atoi(argv[]));

     if(bind(serv_sock,(struct sockaddr*)&serv_adr,sizeof(serv_adr))==-)
         error_handling("bind() error");

     while(){
         clnt_adr_sz=sizeof(clnt_adr);
         str_len=recvfrom(serv_sock,message,BUF_SIZE+,,(struct sockaddr*)&clnt_adr,&clnt_adr_sz);
         message[str_len]=;
         if(message[]==){
             n=message[];
             message[]=message[]=message[]='';
             message[]=;
             for(int i=;i<n;i++){
                 str_len=recvfrom(serv_sock,&message1,BUF_SIZE*,,(struct sockaddr*)&clnt_adr,&clnt_adr_sz);
                 message1[str_len]=;
                 strcat(message,&message1[]);
             }
         }
         if(strlen(&message[])-<=BUF_SIZE){
             message[]=;
             message[]=strlen(&message[]);
             sendto(serv_sock,message,strlen(&message[])+,,(struct sockaddr*)&clnt_adr,clnt_adr_sz);
         }
         else{
             message[]=;
             message[]=strlen(&message[])/BUF_SIZE;
             if(strlen(&message[])%BUF_SIZE!=)
                 message[]+=;
             sendto(serv_sock,message,,,(struct sockaddr*)&clnt_adr,clnt_adr_sz);
             for(int i=;i*BUF_SIZE<strlen(&message[]);i++){
                 message[i*BUF_SIZE]=;
                 message[i*BUF_SIZE+]=i+;
                 message[i*BUF_SIZE+]=BUF_SIZE;
                 if((i+)*BUF_SIZE>strlen(&message[]))
                 message[i*BUF_SIZE+]=strlen(&message[])-i*BUF_SIZE;
                 sendto(serv_sock,&message[i*BUF_SIZE],message[i*BUF_SIZE+]+,,(struct sockaddr*)&clnt_adr,clnt_adr_sz);
             }
         }
     }
     close(serv_sock);
     return ;
 }

 void error_handling(char *message)
 {
     fputs(message,stderr);
     fputc('\n',stderr);
     exit();
 }

echo4_client.c

 #include<stdio.h>
 #include<stdlib.h>
 #include<string.h>
 #include<unistd.h>
 #include<arpa/inet.h>
 #include<sys/socket.h>

 #define BUF_SIZE 10

 void error_handling(char *message);

 int main(int argc,char** argv)
 {
     int sock;
     char message[BUF_SIZE*+],message1[BUF_SIZE+];
     int str_len,n;
     socklen_t adr_sz;

     struct sockaddr_in serv_adr,from_adr;
     if(argc!=){
         printf("Usage : %s <IP> <port>\n",argv[]);
         exit();
     }

     sock=socket(PF_INET,SOCK_DGRAM,);
     if(sock==-)
         error_handling("sock() error");
     memset(&serv_adr,,sizeof(serv_adr));
     serv_adr.sin_family=AF_INET;
     serv_adr.sin_addr.s_addr=inet_addr(argv[]);
     serv_adr.sin_port=htons(atoi(argv[]));

     while(){
         int m_len;
         fputs("Insert message(q to quit): ",stdout);
         fgets(&message[],sizeof(message)-,stdin);
         if(!strcmp(&message[],"q\n")||!strcmp(&message[],"Q\n"))break;
         if(strlen(&message[])-<=BUF_SIZE){
             message[]=;
             message[]=strlen(&message[]);
             sendto(sock,message,strlen(&message[])+,,(struct sockaddr*)&serv_adr,sizeof(serv_adr));
         }
         else{
             message[]=;
             message[]=strlen(&message[])/BUF_SIZE;
             if(strlen(&message[])%BUF_SIZE!=)
                 message[]+=;
             sendto(sock,message,,,(struct sockaddr*)&serv_adr,sizeof(serv_adr));
             for(int i=;i*BUF_SIZE+<strlen(&message[]);i++){
                 message[i*BUF_SIZE]=;
                 message[i*BUF_SIZE+]=i+;
                 message[i*BUF_SIZE+]=BUF_SIZE;
                 if((i+)*BUF_SIZE>=strlen(&message[]))
                 message[i*BUF_SIZE+]=strlen(&message[])--i*BUF_SIZE;
                 sendto(sock,&message[i*BUF_SIZE],message[i*BUF_SIZE+]+,,(struct sockaddr*)&serv_adr,sizeof(serv_adr));
             }
         }

         str_len=recvfrom(sock,message,BUF_SIZE+,,(struct sockaddr*)&from_adr,&adr_sz);
         message[str_len]=;
         if(message[]==){
             n=message[];
             message[]=message[]=message[]='';
             message[]=;
             for(int i=;i<n;i++){
                 str_len=recvfrom(sock,&message1,BUF_SIZE*,,(struct sockaddr*)&from_adr,&adr_sz);
                 message1[str_len]=;
                 strcat(message,&message1[]);
                 //printf("%d,%d,%d,%s\n",message1[0],message1[1],message1[2],&message1[3]);
             }
         }
         printf("Message from server : %s \n",&message[]);
     }
     close(sock);
     return ;
 }

 void error_handling(char *message)
 {
     fputs(message,stderr);
     fputc('\n',stderr);
     exit();
 }