소켓 네트워크 프로그래밍) UDP 소켓 기본 통신

책 ) 뇌를 자극하는 TCP/IP 소켓 프로그래밍

TCP 와는 달리 Clinet 측에서는 Connect가 할 필요가 없고, Server쪽에서는 Listen, Accept를 할 필요가 없다.

왜냐하면 UDP는 데이터를 그냥 보내기 때문이다.

 

#DummyClient(UDP)
#pragma warning(disable:4996)

#include<stdio.h>
#include<iostream>
#include<Winsock2.h>
#pragma comment(lib, "ws2_32.lib")

#define PORT	3600
#define IP		"127.0.0.1"
#define MAXLEN	256

void HandleError(const char* cause) {
	int errCode = ::WSAGetLastError();
	std::cout << cause << "Error Code : " << errCode << std::endl;
}

struct cal_data {
	int left_num;
	int right_num;
	char op;
	int result;
	short int error;
};

int main() {
	SOCKADDR_IN addr;
	SOCKET s;
	WSADATA wsaData;
	char msg[MAXLEN];
	int sbyte, rbyte;
	int left_num, right_num;
	int addrlen;
	char op = NULL;
	struct cal_data sdata;
	ZeroMemory((void*)&sdata, sizeof(sdata));

	if (::WSAStartup(MAKEWORD(2, 0), &wsaData) != 0)
		HandleError("WSAStartup");

	s = socket(AF_INET, SOCK_DGRAM, 0);
	if (s == INVALID_SOCKET)
		HandleError("socket");

	addr.sin_family = AF_INET;
	addr.sin_addr.S_un.S_addr = inet_addr(IP);
	addr.sin_port = ::htons(PORT);

	while (1) {
		printf("> ");
		fgets(msg, MAXLEN - 1, stdin);
		if (strncmp(msg, "quit\n", 5) == 0)
			break;
		sscanf(msg, "%d %c %d", &left_num, &op, &right_num);
		memset((void*)&sdata, 0x00, sizeof(sdata));
		sdata.left_num = htonl(left_num);
		sdata.right_num = htonl(right_num);
		sdata.op = op;

		addrlen = sizeof(addr);
		sbyte = ::sendto(s, (char*)&sdata, sizeof(sdata), 0, (struct sockaddr*)&addr, addrlen);
		rbyte = recvfrom(s, (char*)&sdata, sizeof(sdata), 0, (struct sockaddr*)&addr, &addrlen);

		printf("%d %c %d = %d \n", ntohl(sdata.left_num),
			sdata.op, ntohl(sdata.right_num), ntohl(sdata.result));
	}
	::closesocket(s);
	WSACleanup();
}

---

#DummyServer(UDP)
#pragma warning(disable:4996)

#include<stdio.h>
#include<iostream>
#include<Winsock2.h>
#include<string.h>
#include<io.h>

#pragma comment(lib, "ws2_32.lib")
#define PORT	3600

void HandleError(const char* cause) {
	int errCode = ::WSAGetLastError();
	std::cout << cause << "Error Code : " << errCode << std::endl;
}

struct cal_data {
    int left_num;
    int right_num;
    char op;
    int result;
    short int error;
};

int main()
{
    WSADATA wsaData;
    SOCKET sockfd;
    SOCKADDR_IN sock_addr, client_addr;
    int addr_len;
    int left_num, right_num;
    short int cal_result = 0;
    struct cal_data rdata;
    
    if (WSAStartup(MAKEWORD(2, 2), &wsaData) != 0)
        HandleError("WSAStartup");

    sockfd = socket(AF_INET, SOCK_DGRAM, 0);
    if (sockfd == INVALID_SOCKET)
        HandleError("socket");

    ZeroMemory(&sock_addr, sizeof(struct sockaddr_in));

    sock_addr.sin_family = AF_INET;
    sock_addr.sin_port = htons(PORT);
    sock_addr.sin_addr.S_un.S_addr = htonl(INADDR_ANY);

    addr_len = sizeof(sock_addr);
    if (bind(sockfd, (struct sockaddr*)&sock_addr, addr_len) == SOCKET_ERROR)
    {
        HandleError("Bind");
        return 1;
    }

    while (1)
    {
        addr_len = sizeof(client_addr);
        recvfrom(sockfd, (char*)&rdata, sizeof(rdata), 0, (struct sockaddr *)&client_addr, &addr_len);
#if DEBUG
        printf("Client Info : %s (%d)\n", inet_ntoa(client_addr.sin_addr), ntohs(client_addr.sin_port));
        printf("%d %c %d\n", ntohl(rdata.left_num), rdata.op, ntohl(rdata.right_num));
#endif // DEBUG

        left_num = ntohl(rdata.left_num);
        right_num = ntohl(rdata.right_num);

        switch (rdata.op) {
        case '+':
            cal_result = left_num + right_num;
            break;
        case '-':
            cal_result = left_num - right_num;
            break;
        case '*':
            cal_result = left_num * right_num;
            break;
        case '/':
            cal_result = left_num / right_num;
            break;
        default:
            rdata.error = 1;
        }
        std::cout << "cal_result : " << cal_result << std::endl;
        rdata.result = htonl(cal_result);
        rdata.error = htonl(cal_result);

        sendto(sockfd, (char*)&rdata, sizeof(rdata), 0,(struct sockaddr*)&client_addr, addr_len);
    }

    closesocket(sockfd);
    WSACleanup();
    return 0;
}