[Linux, C] UDP echo 서버, 클라이언트

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/socket.h>

#define BUF_SIZE 30

void error_handling(char *message);

int main(int argc, char *argv[]){
        int serv_sock;
        char message[BUF_SIZE];
        int str_len;
        socklen_t clnt_adr_sz;

        struct sockaddr_in serv_adr, clnt_adr;

        if(argc!=2){
                printf("Usage:%s <port>\n", argv[0]);
                exit(1);
        }

        serv_sock = socket(PF_INET, SOCK_DGRAM, 0);
        if(serv_sock == -1)
                error_handling("UDP socket creation error");

        memset(&serv_adr, 0, sizeof(serv_adr));
        serv_adr.sin_family=AF_INET;
        serv_adr.sin_addr.s_addr=htonl(INADDR_ANY);
        serv_adr.sin_port=htons(atoi(argv[1]));

        if(bind(serv_sock, (struct sockaddr*)&serv_adr, sizeof(serv_adr)) == -1)
                error_handling("bind() error");

        while(1){
                clnt_adr_sz = sizeof(clnt_adr);
                str_len = recvfrom(serv_sock, message, BUF_SIZE, 0, (struct sockaddr*)&clnt_adr, &clnt_adr_sz);
                sendto(serv_sock, message, str_len, 0, (struct sockaddr*)&clnt_adr, clnt_adr_sz);
        }
        close(serv_sock);
        return 0;
}

void error_handling(char *message){
        fputs(message, stderr);
        fputc('\n', stderr);
        exit(1);
}

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/socket.h>

#define BUF_SIZE 30

void error_handling(char *message);

int main(int argc, char *argv[]){
        int sock;
        char message[BUF_SIZE];
        int str_len;
        socklen_t adr_sz;

        struct sockaddr_in serv_adr, from_adr;
        if(argc!=3){
                printf("Usage : %s <IP> <port> \n", argv[0]);
                exit(1);
        }

        sock = socket(PF_INET, SOCK_DGRAM, 0);
        if(sock==-1)
                error_handling("socket() error");

        memset(&serv_adr, 0, sizeof(serv_adr));
        serv_adr.sin_family=AF_INET;
        serv_adr.sin_addr.s_addr=inet_addr(argv[1]);
        serv_adr.sin_port=htons(atoi(argv[2]));

        while(1){
                fputs("Insert message(q to quit):", stdout);
                fgets(message, sizeof(message),stdin);
                if(!strcmp(message, "q\n") || !strcmp(message, "Q\n"))
                        break;

                sendto(sock, message, strlen(message), 0, (struct sockaddr*)&serv_adr,sizeof(serv_adr));

                adr_sz = sizeof(from_adr);
                str_len = recvfrom(sock,message, BUF_SIZE, 0, (struct sockaddr*)&from_adr, &adr_sz);

                message[str_len] = 0;
                printf("Message from server : %s", message);
        }
        close(sock);
        return 0;
}

void error_handling(char *message){
        fputs(message, stderr);
        fputc('\n',stderr);
        exit(1);
}