#include <iostream>using namespace std;#include <sys/socket.h>#include <arpa/inet.h>#include <netinet/in.h>#include <unistd.h>#include <fcntl.h>#include <cstring>#include <signal.h>#include <sys/wait.h>void err(const char* msg){	cout << msg << " error!" << endl;	exit(-1);}void func(int sig){	signal(sig, func);	while(waitpid(-1,NULL,WNOHANG)>0);}int main(){	signal(SIGCHLD, func);	short port;	cout << "input port:";	cin >> port;	sockaddr_in si;	si.sin_family = AF_INET;	si.sin_addr.s_addr = htonl(INADDR_ANY);	si.sin_port = htons(port);	int s = socket(AF_INET,SOCK_STREAM,0);	if(s<0) err("socket");	socklen_t len=sizeof(si);	if(bind(s, (sockaddr*)&si, len)<0)		err("bind");	if(listen(s, 20)<0)		err("listen");	for(;;){		int c=accept(s,(sockaddr*)&si,&len);		if(c<0) continue;		if(fork()!=0){			close(c);			continue;		}		close(s);		char buf[1000]="Your IP: ";		char ip[100];		inet_ntop(AF_INET,&si.sin_addr,ip,100);		strcat(buf, ip);		strcat(buf, "\n");		cout << ip << "到此一游" << endl;		write(c, buf, strlen(buf));		close(c);		exit(0);	}}