[C/linux] UDP Serve/Client socket programming Example

//SERVER

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

#define MAXBUF 256

int main()
{
        int ssock;
        int clen;
        struct sockaddr_in client_addr, server_addr;
        char buf[MAXBUF];

        if((ssock = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP))<0) {
                perror("socket error : ");
                exit(1);
        }

        memset(&server_addr, 0 , sizeof(server_addr));
        server_addr.sin_family = AF_INET;
        server_addr.sin_addr.s_addr = htonl(INADDR_ANY);
        server_addr.sin_port = htons(3317);

        if(bind(ssock, (struct sockaddr*)&server_addr, sizeof(server_addr))<0)
        {
                perror("bind errer : ");
                exit(1);
        }

        recvfrom(ssock, (void*)buf, MAXBUF, 0, (struct sockaddr*)&client_addr, &clen);

        strcpy(buf, "I hate you");

        sendto(ssock, (void*)buf, MAXBUF, 0, (struct sockaddr*)&client_addr,
        sizeof(client_addr));

        close(ssock);

        return 0;
}

//CLIENT

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

#define MAXBUF 256

int main(){
        int ssock;
        int clen;
        struct sockaddr_in client_addr, server_addr;
        char buf[MAXBUF];

        strcpy(buf, "I miss you alerady");

        if((ssock = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP))< 0){
                perror("socket error :");
                exit(1);
        }

        memset(&server_addr, 0, sizeof(server_addr));
        server_addr.sin_family = AF_INET;
        server_addr.sin_addr.s_addr = inet_addr("127.0.0.1");
        server_addr.sin_port = htons(3317);

        sendto(ssock, (void*)buf, MAXBUF, 0,
        (struct sockaddr*)&server_addr, sizeof(server_addr));

        printf("Send message : %s\n, buf");

        recvfrom(ssock, (void*)buf, MAXBUF, 0,
        (struct sockaddr*)&client_addr, &clen);

        printf("Receive message : %s\n", buf);

        close(ssock);

        return 0;
}