C network server programming on linux - c

Question

I would like to make program so that, when client disconnected, the server will back ready to accept a new request from client. Here is the code
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <time.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#define MAXLINE 100
#define LISTENQ 10
int main()
{
int tmp, listenfd, connfd;
int sin_size;
struct sockaddr_in servaddr, cliaddr;
char buff[MAXLINE];
time_t ticks;
while(true)
{
bzero(&servaddr, sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_addr.s_addr = INADDR_ANY;
servaddr.sin_port = htons(13);
memset(&(servaddr.sin_zero),'\0',8);
listenfd = socket(AF_INET, SOCK_STREAM, 0);
if(listenfd == -1){
perror("error socket");
exit(1);
}
tmp=bind(listenfd, (struct sockaddr *)&servaddr, sizeof(struct sockaddr));
if(tmp == -1){
perror("error bind..");
exit(1);
}
tmp=listen(listenfd, LISTENQ);
if(tmp == -1){
perror("error listen");
exit(1);
}
sin_size = sizeof(struct sockaddr_in);
connfd=accept(listenfd,(struct sockaddr *)&cliaddr, &sin_size);
if(connfd == -1){
perror("error accept");
exit(1);
}
ticks = time(NULL);
snprintf(buff,sizeof(buff),"Now Time: %.24s\r\n", ctime(&ticks));
write(connfd, buff, strlen(buff));
close(connfd);
close(listenfd);
}
}
I found a problem on this part
tmp=bind(listenfd, (struct sockaddr *)&servaddr, sizeof(struct sockaddr));
error: invalid conversion from 'int*' to 'socklen_t* {aka unsigned int*}' [-fpermissive]
connfd=accept(listenfd,(struct sockaddr *)&cliaddr, &sin_size);
error: initializing argument 3 of 'int accept(int, sockaddr*, socklen_t*)' [-fpermissive]
What should I do with those problem? Didn't the pointer right?

Answer 1

You need to use
socklen_t sin_size;

Answer 2

Chnage your declaration
socklen_t sin_size;
This solves your issue.
you can also Try this as last resort but above change would works fine for you.
Modify this statement
connfd=accept(listenfd,(struct sockaddr *)&cliaddr,(socklen_t * ) &sin_size);
See man accept
After seeing #alk comment i am adding this part from comment.
Especially when casting pointers, it might just cast away an compile-time error but very well might crash when running as the sizes of what the program expects when Dereferencing the pointer differs from reality.

Answer 3

Use while(1) instead of while(true) and use a C-compiler instead of a C++-compiler.
The errors come from compiling the source code with a C++compiler. If you use a C-Compiler your code does not produce the mentioned errors, except that now true is not defined.

Answer 4

Correct answer, need to run on root-access user
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <time.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdbool.h>
#define MAXLINE 100
#define LISTENQ 10
int main()
{
int tmp, listenfd, connfd;
socklen_t sin_size;
struct sockaddr_in servaddr, cliaddr;
char buff[MAXLINE];
time_t ticks;
while(true)
{
bzero(&servaddr, sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_addr.s_addr = INADDR_ANY;
servaddr.sin_port = htons(13);
memset(&(servaddr.sin_zero),'\0',8);
listenfd = socket(AF_INET, SOCK_STREAM, 0);
if(listenfd == -1){
perror("error socket");
exit(1);
}
tmp=bind(listenfd, (struct sockaddr *)&servaddr, sizeof(struct sockaddr));
if(tmp == -1){
perror("error bind..");
exit(1);
}
tmp=listen(listenfd, LISTENQ);
if(tmp == -1){
perror("error listen");
exit(1);
}
sin_size = sizeof(struct sockaddr_in);
connfd=accept(listenfd,(struct sockaddr *)&cliaddr, &sin_size);
if(connfd == -1){
perror("error accept");
exit(1);
}
ticks = time(NULL);
snprintf(buff,sizeof(buff),"Sekarang pukul: %.24s\r\n", ctime(&ticks));
write(connfd, buff, strlen(buff));
close(connfd);
close(listenfd);
}
}