Connect error in Daytime tcp server in c++

Question

I'm new to network programming and I was following the book "unix network programming, the socket networking api." I was trying the first example of this book, a day time server. I wrote these codes for client and server. I executed the server.cpp from one terminal and client.cpp from another one.(./a.out 127.0.0.1) I'm supposed to get the time as output, but I keep getting connect error. Can someone please help me out?

Client.cpp

#include "unp.h"
int main(int argc, char** argv)
{
int sockfd,n;
struct sockaddr_in servaddr;
char recvline[MAXLINE+1];
if(argc!=2)
{
    err_quit("Usage ./a.out <IPaddress>\n");
}
if((sockfd=socket(AF_INET,SOCK_STREAM,0))<0)
{
    err_quit("Socket error\n");
}
memset(&servaddr,0,sizeof(servaddr));
servaddr.sin_family=AF_INET;
servaddr.sin_port=htons(13);
if(inet_pton(AF_INET,argv[1],&servaddr.sin_addr)<=0)
{
    err_quit("inet_pton error");
}
if(connect(sockfd,(sockaddr *) &servaddr,sizeof(servaddr))<0)
{
    err_quit("connect error\n");
}
while((n=read(sockfd,recvline,MAXLINE))>0)
{
    recvline[n]=0;
    if(fputs(recvline,stdout)==EOF)
    {
        err_quit("fputs error\n");
    }
}
if(n<0)
{
    err_quit("read error\n");
}
exit(0);
return 0;
}

server.cpp

#include "unp.h"
int main(int argc,char** argv)
{
    int listenfd,connfd;
    struct sockaddr_in servaddr;
    char buff[MAXLINE];
    time_t ticks;
    listenfd=socket(AF_INET,SOCK_STREAM,0);
    memset(&servaddr,0,sizeof(servaddr));
    servaddr.sin_family=AF_INET;
    servaddr.sin_addr.s_addr=htonl(INADDR_ANY);
    servaddr.sin_port=htons(13);
    bind(listenfd,(sockaddr *)&servaddr,sizeof(servaddr));
    listen(listenfd,LISTENQ);
    for(;;)
    {
        connfd=accept(listenfd, (sockaddr *)NULL,NULL);
        ticks=time(NULL);
        snprintf(buff,sizeof(buff),"%.24s\r\n",ctime(&ticks));
        write(connfd,buff,strlen(buff));
        close(connfd);
    }
    exit(0);
}

unp.h

#include<iostream>
#include<stdio.h>
#include<stdlib.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<sys/time.h>
#include<time.h>
#include<sys/wait.h>
#include<sys/un.h>
#include<string.h>
#include<sys/uio.h>
#include<unistd.h>
#include<sys/stat.h>
#include<netdb.h>
#include<signal.h>
#include<fcntl.h>
#include<errno.h>
#include<arpa/inet.h>
#include<netinet/in.h>
#define MAXLINE 4096
#define LISTENQ 1024
using namespace std;
void err_quit(const char *x)
{
    printf("%s",x);
    exit(-1);
}

Answer 1

On UNIX systems only users with superuser authorizations ( "root" ) can bind to ports < 1024. Please try run this version which wrapps a function calls with better error handling/reporting with sudo. Next change port to something >1023 and try again without sudo.

#include "unp.h"

#include <time.h>
#include <assert.h>

int
main(int argc, char **argv) {

    int listenfd, connfd;
    socklen_t len;
    struct sockaddr_in servaddr, cliaddr;
    char buff[MAXLINE];
    time_t ticks;

    listenfd = Socket(AF_INET, SOCK_STREAM, 0);

    bzero(&servaddr, sizeof (servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    servaddr.sin_port = htons( 13); /* test*/

    Bind(listenfd, (SA *) & servaddr, sizeof (servaddr));

    Listen(listenfd, LISTENQ);
    puts("listening...");

    for (;;) {
        len = sizeof (cliaddr);
        connfd = Accept(listenfd, (SA *) & cliaddr, &len);
        printf( "connection from %s, port %d\n",
                Inet_ntop(AF_INET, &cliaddr.sin_addr, buff, sizeof (buff)),
                ntohs(cliaddr.sin_port));

        ticks = time(NULL);
        snprintf(buff, sizeof (buff), "%.24s\r\n", ctime(&ticks));

        //Write(connfd, buff, strlen(buff)); // normal version, write at once
        int i; // call Write for each one byte
        for (i = 0; i < strlen(buff); ++i) {
            Write(connfd, &buff[i], 1);
        }
        printf( "writes: %d\n", i);
        Close(connfd);
    }
}

---

If you can't compile it, then try this:

#include "unp.h"
int main(int argc,char** argv)
{
    int listenfd,connfd;
    struct sockaddr_in servaddr;
    char buff[MAXLINE];
    time_t ticks;
    listenfd=socket(AF_INET,SOCK_STREAM,0);
    memset(&servaddr,0,sizeof(servaddr));
    servaddr.sin_family=AF_INET;
    servaddr.sin_addr.s_addr=htonl(INADDR_ANY);
    servaddr.sin_port=htons(13);
    bind(listenfd,(sockaddr *)&servaddr,sizeof(servaddr));
    listen(listenfd,LISTENQ);
    puts("listening...");
    for(;;)
    {
        connfd=accept(listenfd, (sockaddr *)NULL,NULL);
        puts("accepted...");
        ticks=time(NULL);
        snprintf(buff,sizeof(buff),"%.24s\r\n",ctime(&ticks));
        write(connfd,buff,strlen(buff));
        close(connfd);
    }
    puts("exiting...");
    exit(0);
}