并发反射服务器

#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <time.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <signal.h>

const int maxline = 4096;

size_t writen(int fd, const void *vptr, size_t n) {
        size_t nleft;
        size_t nwritten;
        const char *ptr;

        ptr=vptr;
        nleft=n;
        while(nleft>0) {
                if((nwritten=write(fd, ptr, nleft))<=0) {
                        if(nwritten<0 && errno==EINTR)
                                nwritten=0;
                        else
                                return -1;
                }
                nleft-=nwritten;
                ptr+=nwritten;
        }
        return n;
}

void str_echo(int sockfd) {
	size_t n;
	char buff[maxline];

again:
	while((n=read(sockfd, buff, maxline))>0) {
		if(writen(sockfd, buff, n)!=n) {
			fprintf(stderr, "writen error!\n");
		}
	}
	if(n<0 && errno==EINTR)
		goto again;
	else if(n<0) {
		fprintf(stderr, "read error\n");
		exit(-1);
	}
}

void sig_chld(int signo) {
	pid_t pid;
	int stat;
	
	while((pid=waitpid(-1, &stat, WNOHANG))>0) {
		printf("child %d terminated\n", pid);
	}
	return;
}

int main(int argc, char **argv) {
	int listenfd, connfd;
	socklen_t len;
	pid_t childpid;
	struct sockaddr_in servaddr, cliaddr;
	char buff[maxline], errbuff[maxline];
	time_t ticks;

	if((listenfd=socket(AF_INET, SOCK_STREAM, 0))<0) {
		strerror_r(errno, errbuff, maxline);
		fprintf(stderr, "socket error: %s\n", errbuff);
		exit(-1);
	}
	
	memset(&servaddr, 0, sizeof(servaddr));
	servaddr.sin_family = AF_INET;
	servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
	servaddr.sin_port = htons(9999);

	if(bind(listenfd, (struct sockaddr *)&servaddr, sizeof(servaddr))<0) {
		strerror_r(errno, errbuff, maxline);
		fprintf(stderr, "bind error: %s\n", errbuff);
		exit(-1);
	}

	if(listen(listenfd, 1024)<0) {
		strerror_r(errno, errbuff, maxline);
		fprintf(stderr, "listen error: %s\n", errbuff);
		exit(-1);
	}

	signal(SIGCHLD, sig_chld);
	
	for(;;)	{
		len=sizeof(cliaddr);
		if((connfd=accept(listenfd, (struct sockaddr *)&cliaddr, &len))<0) {
			if(errno == EINTR) {
				continue;
			} else {
				strerror_r(errno, errbuff, maxline);
				fprintf(stderr, "accept error: %s\n", errbuff);
				exit(-1);
			}
		}
		printf("connection from %s, port %d\n", inet_ntop(AF_INET, &cliaddr.sin_addr, buff, sizeof(buff)), ntohs(cliaddr.sin_port));
		if((childpid=fork())<0) {
			strerror_r(errno, errbuff, maxline);
			fprintf(stderr, "fork error: %s\n", errbuff);
			exit(-1);
		} else if(childpid == 0) {
			printf("ppid: %d\n", getppid());
			if(close(listenfd)<0) {
				strerror_r(errno, errbuff, maxline);
				fprintf(stderr, "child pid close listenfd error: %s\n", errbuff);
				exit(-1);
			}
			str_echo(connfd);
			exit(0);
		} else {
			printf("childpid: %d\n", childpid);
			if(close(connfd)<0) {
				strerror_r(errno, errbuff, maxline);
				fprintf(stderr, "parent pid close connfd error: %s\n", errbuff);
				exit(-1);
			}
		}
	}
	return 0;
}