c++ socket tcp one process one thread increase one server and client

one_process_increase_client.cpp

#include <cstdio>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <iostream>

using namespace std;

void error(const char *message){
	perror(message);
	exit(1);
}

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

	if(argc<3)	error("argument is ip and port.");

	int server_socket;
	int port;
	struct hostent *server_url;
	struct sockaddr_in server_addr; 
	string input;
	int check;

	port=atoi(argv[2]);

	server_socket=socket(AF_INET,SOCK_STREAM,0);
	if(server_socket<0) error("error occurs in opening socket."); 

	server_url=gethostbyname(argv[1]); 
	if(server_url<0) error("error occurs, because no such host."); 

	server_addr.sin_family=AF_INET;
	bcopy((char *)server_url->h_addr,(char *)&server_addr.sin_addr.s_addr,server_url->h_length);
	server_addr.sin_port=htons(port);

	check=connect(server_socket,(struct sockaddr *)&server_addr,sizeof(server_addr));
	if(check<0) error("error occurs in connecting");
	
	while(true){
		
		cout<<"input the number: ";
		cin>>input;

		if(string("exit").compare(input) == 0 || string("shutdown").compare(input) == 0){
			cout<<input<<" the server."<<endl;
			write(server_socket, input.c_str(), input.length() );
			close(server_socket);
			exit(0);
		}else{
			try {
				stoi(input);
			} catch(...) {
				cout<<"Try again."<<endl;
				continue;
			}

			check = write(server_socket, input.c_str(), input.length() );
			if(check<0) error("disconnect, server shutdowned.");

			char buffer[256] = { 0 };
			check = read(server_socket,buffer,256);
			if(check<=0) error("disconnect, server shutdowned.");

			cout<<"result: "<<buffer<<endl;
		}
	}

}

one_process_increase_server.cpp

#include <cstdio>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <string.h>
#include <iostream>

using namespace std;

void error(const char *message){
	perror(message);
	exit(1);
}

int main(int argc,char **argv){
		
	if(argc<2)	error("argument is port.");

	int server_socket, client_socket;
	int port;
	socklen_t client_socket_length;
	struct sockaddr_in server_addr,client_addr;
	int queue_length;
	int check;
	
	port=atoi(argv[1]);
	queue_length=128;  

	server_socket=socket(AF_INET,SOCK_STREAM,0);
	if(server_socket<0)	error("error occurs in opening server_socket");

	server_addr.sin_family=AF_INET;
	server_addr.sin_addr.s_addr=INADDR_ANY;
	server_addr.sin_port=htons(port);        

	check = bind(server_socket,(struct sockaddr *)&server_addr,sizeof(server_addr));
	if(check<0) error("error occurs in binding");        
	
	check = listen(server_socket,queue_length);
	if(check<0) error("error occurs in listening");      

	bool isOver = false;
	while(!isOver){
		
		client_socket_length=sizeof(client_addr);
		client_socket=accept(server_socket,(struct sockaddr *)&client_addr,&client_socket_length);

		if(client_socket<0) error("error occurs in accepting");
		else cout<<"client enters."<<endl;
		while(true){
			char buffer[256] = { 0 };

			check = read(client_socket,buffer,256);
			if(check <= 0) {
				cout << "disconnect, client exited." << endl;
				close(client_socket);
				break;
			}else if(string("exit").compare(buffer) == 0){
				cout << "client exited." << endl;
				close(client_socket);
				break;
			}else if(string("shutdown").compare(buffer) == 0){
				cout << "server will shutdown." << endl;
				write(client_socket,"shutdown",9);
				close(client_socket);
				isOver = true;
				break;
			}
			int output = 0;
			string message;
			try {
				output = stoi(buffer) + 1;

				cout<<"client: "<<buffer<<endl;
				cout<<"result: "<<output<<endl;

				message=to_string(output);
			} catch(...) {
				message="Try again, input number.";
			}
			check=write(client_socket,message.c_str(),message.length());
			if(check<0){
				cout << "disconnect, client exited." << endl;
				close(client_socket);
				break;
			}
		}
	}
	close(server_socket);
	close(client_socket);
	return 0;
}