Question

//SERVER SIDE SCRIPT for Deffie Hellman using sockets.

#include<stdio.h>
#include<netinet/in.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<netdb.h>
#include<string.h>
#include<math.h>
#include<stdlib.h>
#define MAX 80
#define PORT 43461
#define SA struct sockaddr



char* itoa(int value, char* str, int radix) {
    static char dig[] =
        "0123456789"
        "abcdefghijklmnopqrstuvwxyz";
    int n = 0, neg = 0;
    unsigned int v;
    char* p, *q;
    char c;
    if (radix == 10 && value < 0) {
        value = -value;
        neg = 1;
    }
    v = value;
    do {
        str[n++] = dig[v%radix];
        v /= radix;
    } while (v);
    if (neg)
        str[n++] = '-';
    str[n] = '\0';
    for (p = str, q = p + (n-1); p < q; ++p, --q)
        c = *p, *p = *q, *q = c;
    return str; 
}

void func(int sockfd) 
{
    printf("hello"); //This statement is not being displayed and rest of the code not    executed
    char buff[MAX],uname[MAX],pass[MAX];
    int n,clen,a1,a2,b2,val,key;
    struct sockaddr_in cli;
    clen=sizeof(cli);

xx: 

    //RECIEVING USERNAME
    bzero(uname,MAX);
    recvfrom(sockfd,uname,sizeof(buff),0,(SA *)&cli,&clen);
    printf("Username recieved");
    //RECIEVING PASSWORD
    bzero(pass,MAX);
    recvfrom(sockfd,pass,sizeof(buff),0,(SA *)&cli,&clen);

    if(strcmp(uname,"admin") == 10 && strcmp(pass,"admin") == 10)
    {

        printf("Accepted");

        //RECIEVING NUMBER FROM CLIENT
        recvfrom(sockfd,buff,sizeof(buff),0,(SA *)&cli,&clen);
        b2=atoi(buff);

        printf("Recieved from client\n");

        //GENERATING SERVER SIDE NUMBER
        a1=(rand() % 19) + 1; // Random value selected by Server
        a2=pow(7,a1);   
        a2=a2 % 11;   // Server Generating value to be sent G:7 , P:11

        //Sending the value-a2
        bzero(uname,MAX);
        itoa(a2,buff,10);
        sendto(sockfd,buff,sizeof(buff),0,(SA *)&cli,clen);
        printf("Server side number sent\n");

        //GENERATING KEY AND THE DATA
        key=pow(b2,a1); 
        key=key % 11;       //                      G:7 , P:11
        val=key*1024;          //                       DATA: 7060

        //Sending the data required
        bzero(uname,MAX);
        itoa(a1,buff,10);
        sendto(sockfd,buff,sizeof(buff),0,(SA *)&cli,clen); 
        printf("Data sent \n");     
    }
    else
    {
        printf("Incorrect Username-Password combination. Waiting for next try \n");
        strcpy(buff,"wrong");
        sendto(sockfd,buff,sizeof(buff),0,(SA *)&cli,clen);
        goto xx;

    }
}


int main()
{
    int sockfd;
    struct sockaddr_in servaddr;
    sockfd=socket(AF_INET,SOCK_DGRAM,0);
    if(sockfd==-1)
    {
        printf("socket creation failed...\n");
        exit(0);
    }
    else
        printf("Socket successfully created..\n");
    bzero(&servaddr,sizeof(servaddr));
    servaddr.sin_family=AF_INET;
    servaddr.sin_addr.s_addr=htonl(INADDR_ANY);
    servaddr.sin_port=htons(PORT);
    if((bind(sockfd,(SA *)&servaddr,sizeof(servaddr)))!=0)
    {
        printf("socket bind failed...\n");
        exit(0);
    }
    else
    {
        printf("%d",sockfd);// This value is displayed in the output screen
        printf("Socket successfully binded..\n");}
        func(sockfd);
        close(sockfd);
    }

执行脚本时，绑定成功完成，输出屏幕上显示相同的消息。但是没有执行函数调用func（）。我没有得到函数调用的第一个语句 - ＆＃39;你好＆＃39;在执行中。请建议此代码中所需的更改。

Answer 1

如果bind()成功，则会调用func()。您没有看到输出的原因是因为stdout通常是缓冲的，并且一旦内部缓冲区已满，它将刷新它。

将\n添加到调试printf()调用中，这将强制它刷新输出。

printf("hello\n");

同样，其他调试printf＆＃39>。您还可以使用fflush(stdout);来刷新stdout。

显然，您需要客户端代码，因为服务器正在您的代码中等待它。

代码编译成功但func（）没有被执行。有人请建议所需的更改

1 个答案: