12. UDP

 

12. 1. Server UDP Socket

#include<stdio.h> 
#include<stdlib.h> 
#include<sys/types.h> 
#include<netinet/in.h> 
#include<inttypes.h>
#include<sys/socket.h> 
#include<arpa/inet.h> 
#include<string.h> 
#include<unistd.h>

#define PORTNUM 1234

int main(void){
    char buf[256];
    struct sockaddr_in sin, cli;
    int sd, ns, clientlen = sizeof(cli);

    if((sd = socket(AF_INET, SOCK_STREAM, 0)) == -1){
        perror("socket");
        exit(1);
    }
    
    memset((char *)&sin, '\0', sizeof(sin));
    sin.sin_family = AF_INET;
    sin.sin_port = htons(PORTNUM);
    sin.sin_addr.s_addr = inet_addr("0.0.0.0"); // 0.0.0.0은 모든 IP로부터의 요청을 받는다는 뜻.

    if(bind(sd, (struct sockaddr *)&sin, sizeof(sin))){
        perror("bind");
        exit(1);
    }
    
    while (1) {
    	if ((recvfrom(sd, buf, 255, 0,
 				(struct sockaddr *)&cli, &clientlen)) ==-1) {
			perror("recvfrom");
            exit(1);
        }
        
        printf("** From Client : %s\n", buf);
        strcpy(buf, "Hello Client");
        
 		if ((sendto(sd, buf, strlen(buf)+1, 0,
       			(struct sockaddr *)&cli, sizeof(cli))) == -1) {
 			perror("sendto");
 			exit(1);
 		}
 	}
    
    return 0;
}

 

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12. 2. Client UDP Socket

 

#include<stdio.h> 
#include<stdlib.h> 
#include<sys/types.h> 
#include<netinet/in.h> 
#include<inttypes.h>
#include<sys/socket.h> 
#include<arpa/inet.h> 
#include<string.h> 
#include<unistd.h>
#define PORTNUM 1234

int main(void){
    int sd;
    char buf[256];
    struct sockaddr_in sin;

    if((sd = socket(AF_INET, SOCK_STREAM, 0)) == -1){
        perror("socket");
        exit(1);
    }

    memset((char *)&sin, '\0', sizeof(sin));
    sin.sin_family=AF_INET;
    sin.sin_port = htons(PORTNUM);
    sin.sin_addr.s_addr = inet_addr("0.0.0.0"); // 정확한 포트명 입력하기
    
    strcpy(buf,"I am a client.");
    
    if (sendto(sd,buf,strlen(buf)+1,0,
    		(structsockaddr*)&sin,sizeof(sin)) ==-1){
    	perror("sendto");
        exit(1);
    }
    
    n = recvfrom(sd, buf, 255, 0, NULL, NULL);
    buf[n] = '\0';
    printf("** From Server : %s\n", buf);
    
    return 0;
}

 

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