UDP Client/Server

int UDP_Open(int port)

{

        int sd;

        if((sd = socket(AF_INET,SOCK_DGRAM,0)) == -1) return -1;

        struct sockaddr_in myaddr;

        bzero(&myaddr,sizeof(myaddr));    

        myaddr.sin_family = AF_INET;

        myaddr.sin_port = htons(port);

        myaddr.sin_addr.s_addr = INADDR_ANY;

        if(bind(sd,(struct sockaddr*)&myaddr,sizeof(myaddr)) == -1)

        {

                close(sd);

                return -1;

        }

        return sd;

}

int UDP_FillSockAddr(struct sockaddr_in *addr,char *hostName, int port)

{

        bzero(addr,sizeof(struct sockaddr_in));

        addr->sin_family = AF_INET;

        addr->sin_port = htons(port);

        struct in_addr *inAddr;

        struct hostent *hostEntry;    

        if((hostEntry = gethostbyname(hostName)) == NULL) return -1;

        inAddr = (struct in_addr*) hostEntry->h_addr;

        addr->sin_addr = *inAddr;

        return 0;

}

int UDP_Write(int sd, struct sockaddr_in *addr, char *buffer, int n)

{

        int addrLen = sizeof(struct sockaddr_in);

        return sendto(sd,buffer,n,0, (struct sockaddr *)addr,addrLen);

}

int UDP_Read(int sd, struct sockaddr_in *addr, char *buffer, int n)

{

        int len = sizeof(struct sockaddr_in);

        return recvfrom(sd,buffer,n,0,(struct sockaddr *) addr,(socklen_t *) &len);

}

// client code

int main(int argc, char *argv[])

{

        int sd = UDP_Open(2000);

        struct sockaddr_in addr, addr2;

        int rc = UDP_FillSockAddr(&addr,"machine.cs.wisc.edu",10000);

        char message[BUFFER_SIZE];

        sprintf(message, "hello world");

        rc = UDP_Write(sd,&addr,message,BUFFER_SIZE);

        if(rc > 0)

        {

                rc = UDP_Read(sd,&addr2,buffer,BUFFER_SIZE);

        }

        return 0;

}

// server code

int main(int argc, char *argv[])

{

        int sd = UDP_Open(10000);

        assert(sd > -1);

        while(1)

        {

                struct sockaddr_in s;

                char buffer[BUFFER_SIZE];

                int rc = UDP_Read(sd, &s, buffer, BUFFER_SIZE);

                if(rc > 0)

                {

                        char reply[BUFFER_SIZE];

                        sprintf(reply,"reply");

                        rc = UDP_Write(sd, &s, reply, BUFFER_SIZE);

                }

        }

        return 0;

}