#include <netinet/in.h>
//from host byte order to network byte order
uint16_t htons(uint16_t  host16bitvalue)//servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
uint32_t htonl(uint32_t  host32bitvalue)//from network byte order to host byte order
uint16_t ntohs(uint16_t  host16bitvalue)
uint16_t ntohl(uint16_t  host16bitvalue)

#include <arpa/inet.h>int inet_pton(int family, const char* strptr, void *addrptr);　　//成功返回1，格式错误返回0，出错返回-1//示例：：Inet_pton(AF_INET, argv[1], &serveraddr.sin_addr);const char* inet_ntop(int family, const void*addrptr, char *strptr, size_t len); //len参数指出缓存区的大小，避免出现溢出

#include "unp.h"
#include <stdio.h>
#include <stdlib.h>void str_echo(int sockfd);
Sigfunc* signal1(int signo, Sigfunc* func);
void sig_child(int signo);
int main(int argc, char** argv){int listenfd, connfd;char buff[MAXLINE];pid_t childpid;socklen_t clilen;struct sockaddr_in cliaddr, servaddr;//<sys/socket.h>//int socket(int family, int type, int protocal);listenfd = Socket(AF_INET, SOCK_STREAM, 0);bzero(&servaddr, sizeof(struct sockaddr_in));servaddr.sin_family = AF_INET;servaddr.sin_addr.s_addr = htonl(INADDR_ANY);servaddr.sin_port = htons(SERV_PORT);Bind(listenfd, (SA*) &servaddr, sizeof(servaddr));Listen(listenfd, LISTENQ);//working with the
    signal1(SIGCHLD, sig_child);while(1){clilen = sizeof(cliaddr);connfd = Accept(listenfd, (SA*)&cliaddr, &clilen);if ((childpid = Fork()) == 0){Close(listenfd);str_echo(connfd);exit(0);}Close(connfd);}return 0;
}void str_echo(int sockfd){ssize_t n;char buf[MAXLINE];
again:while((n = read(sockfd, buf, MAXLINE) ) > 0)Write(sockfd, buf, n);if (n < 0 && errno == EINTR)goto again;else if (n < 0)err_sys("str_echo: read error");}Sigfunc* signal1(int signo, Sigfunc* func){struct sigaction act, oact;act.sa_handler = func;sigemptyset(&act.sa_mask);act.sa_flags = 0;if ( signo == SIGALRM){
#ifdef SA_INTERRUPT//设定中断,使该信号处理过程中能够中断:act.sa_flags |= SA_INTERRUPT;
#endif}else{
#ifdef    SA_RESTART//信号处理，设置SA_RESTART标志，使得内核对失败的//系统调用自动重启。act.sa_flags |= SA_RESTART;
#endif}if (sigaction(signo, &act, &oact) < 0){return SIG_ERR;}return (oact.sa_handler);
}void sig_child(int signo){pid_t pid;int stat;/***********************************************
#inlcude <sys/wait.h>这里使用wait函数只能处理第一个返回的僵死进程，因为其UNIX系统信号实现中信号是不进行排队的。所以我们采用waitpid并且设定最后的选项为WNOHANG.表示内核在没有进程时不仅行阻塞。***********************************************///  --- pid = wait(&stat);while(( pid = waitpid(-1, &stat, WNOHANG)) > 0)printf("child %d terminated.\n", pid);return;
}

#include "unp.h"
#include <stdio.h>
#include <stdlib.h>int str_cli1(FILE *fp, int sockfd);int main(int argc, char** argv){int sockfd[5];struct sockaddr_in serveraddr;int i;if (argc < 2)err_quit("Use: clisocket <IPaddress>");for (i = 0; i <5; ++i){sockfd[i] = Socket(AF_INET, SOCK_STREAM,0);bzero(&serveraddr, sizeof(struct sockaddr_in));serveraddr.sin_family = AF_INET;serveraddr.sin_port = htons(SERV_PORT);Inet_pton(AF_INET, argv[1], &serveraddr.sin_addr);Connect(sockfd[i], (SA*)&serveraddr, sizeof(serveraddr));}str_cli(stdin, sockfd[0]);exit(0);
}int str_cli1(FILE *fp, int sockfd){char sendline[MAXLINE], recvline[MAXLINE];while(Fgets(sendline, MAXLINE, fp) != NULL){Writen(sockfd, sendline, strlen(sendline));if (Readline(sockfd, recvline, MAXLINE) == 0)err_quit("str_cli: server terminated prematurely");Fputs(recvline, stdout);}
}