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*8+3],message1[BUF_SIZE+3]; 
    int str_len;
    socklen_t clnt_adr_sz;
    struct sockaddr_in serv_adr,clnt_adr;
    if(argc!=2){
        printf("Usage : %s <port>
",argv[0]);
        exit(1);
    }
    serv_sock=socket(PF_INET,SOCK_DGRAM,0);
    if(serv_sock == -1){
        error_handling("UDP socket creattion error");
    }

    memset(&serv_adr,0,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[1]));

    if(bind(serv_sock,(struct sockaddr*)&serv_adr,sizeof(serv_adr))==-1)
        error_handling("bind() error");

    while(1){
        clnt_adr_sz=sizeof(clnt_adr);
        str_len=recvfrom(serv_sock,message,BUF_SIZE+3,0,(struct sockaddr*)&clnt_adr,&clnt_adr_sz);
        message[str_len]=0;
        if(message[0]==0){
            n=message[1];
            message[0]=message[1]=message[2]='1';
            message[3]=0;
            for(int i=0;i<n;i++){
                str_len=recvfrom(serv_sock,&message1,BUF_SIZE*2,0,(struct sockaddr*)&clnt_adr,&clnt_adr_sz);
                message1[str_len]=0;
                strcat(message,&message1[3]);
            }
        }
        if(strlen(&message[3])-1<=BUF_SIZE){
            message[0]=1;
            message[2]=strlen(&message[3]);
            sendto(serv_sock,message,strlen(&message[3])+3,0,(struct sockaddr*)&clnt_adr,clnt_adr_sz);
        }
        else{
            message[0]=0;
            message[1]=strlen(&message[3])/BUF_SIZE;
            if(strlen(&message[3])%BUF_SIZE!=0)
                message[1]+=1;
            sendto(serv_sock,message,2,0,(struct sockaddr*)&clnt_adr,clnt_adr_sz);
            for(int i=0;i*BUF_SIZE<strlen(&message[3]);i++){
                message[i*BUF_SIZE]=2;
                message[i*BUF_SIZE+1]=i+1;
                message[i*BUF_SIZE+2]=BUF_SIZE;
                if((i+1)*BUF_SIZE>strlen(&message[3]))
                message[i*BUF_SIZE+2]=strlen(&message[3])-i*BUF_SIZE;
                sendto(serv_sock,&message[i*BUF_SIZE],message[i*BUF_SIZE+2]+3,0,(struct sockaddr*)&clnt_adr,clnt_adr_sz);
            }
        }
    }
    close(serv_sock);
    return 0;
}

void error_handling(char *message)
{
    fputs(message,stderr);
    fputc('
',stderr);
    exit(1);
}

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*8+3],message1[BUF_SIZE+3];
    int str_len,n;
    socklen_t adr_sz;

    struct sockaddr_in serv_adr,from_adr;
    if(argc!=3){
        printf("Usage : %s <IP> <port>
",argv[0]);
        exit(1);
    }

    sock=socket(PF_INET,SOCK_DGRAM,0);
    if(sock==-1)
        error_handling("sock() error");
    memset(&serv_adr,0,sizeof(serv_adr));
    serv_adr.sin_family=AF_INET;
    serv_adr.sin_addr.s_addr=inet_addr(argv[1]);
    serv_adr.sin_port=htons(atoi(argv[2]));

    while(1){
        int m_len;
        fputs("Insert message(q to quit): ",stdout);
        fgets(&message[3],sizeof(message)-3,stdin);
        if(!strcmp(&message[3],"q
")||!strcmp(&message[3],"Q
"))break;
        if(strlen(&message[3])-1<=BUF_SIZE){
            message[0]=1;
            message[2]=strlen(&message[3]);
            sendto(sock,message,strlen(&message[3])+3,0,(struct sockaddr*)&serv_adr,sizeof(serv_adr));
        }
        else{
            message[0]=0;
            message[1]=strlen(&message[3])/BUF_SIZE;
            if(strlen(&message[3])%BUF_SIZE!=0)
                message[1]+=1;
            sendto(sock,message,2,0,(struct sockaddr*)&serv_adr,sizeof(serv_adr));
            for(int i=0;i*BUF_SIZE+1<strlen(&message[3]);i++){
                message[i*BUF_SIZE]=2;
                message[i*BUF_SIZE+1]=i+1;
                message[i*BUF_SIZE+2]=BUF_SIZE;
                if((i+1)*BUF_SIZE>=strlen(&message[3]))
                message[i*BUF_SIZE+2]=strlen(&message[3])-1-i*BUF_SIZE;
                sendto(sock,&message[i*BUF_SIZE],message[i*BUF_SIZE+2]+3,0,(struct sockaddr*)&serv_adr,sizeof(serv_adr));
            }
        }

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

void error_handling(char *message)
{
    fputs(message,stderr);
    fputc('
',stderr);
    exit(1);
}