UDP server/ client exchange bulletin

**markovn** · 10-22-2011

Hi everyone! I'm a freshman in our forum. To the beginning, hope all of you have a nice day

.
I'm having an assignment about UDP server client which exchange their bulletin to each other. Similar my code below i successfully ran completely with TCP. However, i can't figure out what is the reason why my code does not work

. I'm totally clueless now.
Here is my code :

server:

Code:

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

int main(int argc,char* argv[])
{
//---------------- tao cac struct ban tin----------
 struct hello {
char hello_id[11];//10 ky tu dientu-k53 + 1 ki tu ket thuc
long int hello_len; //32bit
long int hello_detect;
char mail_user[50];    //mail user from client
} HEL;
HEL.hello_detect=0;

struct acknowledgement {
char ack_id[11];
long int ack_len;

long int ack_detect;
char client_mail[50];    //tra ve mail user cho client
char ack_state[20];     //trang thai "success" or "failed"
} ACK;
strcpy(ACK.ack_id,"dientu-K53");
ACK.ack_detect=1;
//char ack_state[];        //vua thay doi

struct bye {
char bye_id[11];
long int bye_detect;
} BYE;
strcpy(BYE.bye_id,"dientu-K53");
BYE.bye_detect=2;

int dem=0;

//----------ket thuc tao ban tin -----------------

int serverSocket;
serverSocket=socket(PF_INET,SOCK_DGRAM,0);
if(serverSocket==-1)
{
perror("UDP server socket !!! \n");
close(serverSocket);
exit(1);
}

int i=1;  //option for enabling reuse option below
int check;
/*check=setsockopt(serverSocket,SOL_SOCKET,SO_REUSEADDR,&i,sizeof(int));
if(check=-1)
{
perror("failed to set reuse\n");
    
}    */  
//---------loading socket address structure------------
struct sockaddr_in serverAddress;
//struct sockaddr_in clientAddress;
serverAddress.sin_family=AF_INET;
serverAddress.sin_port=htons(5011);
serverAddress.sin_addr.s_addr=INADDR_ANY;
//socklen_t len=sizeof (struct sockaddr_in);
//-------------------define length of clientaddr , serveraddr--------------------
//int clientaddrlen=sizeof(clientAddress);
int serveraddrlen=sizeof(serverAddress);

check=bind(serverSocket,(struct sockaddr *)&serverAddress,serveraddrlen);
if(bind==-1)
{
perror("failed to bind socket address structure\n");
close(serverSocket);
exit(0);
}         //gia tri tra ve cua bind trong UDP connectionless la con tro        

else {//--------------DATA handling begin ----------------------
printf("chuan bi xu ly \n");
//------------------------Declare prototypes-------------------------
//struct sockaddr_in clientAddress;
//len=sizeof(struct sockaddr_in);
fd_set readfds;        //check sockets ready for reading
fd_set masterfds;     //luu thay doi cua readfds
FD_ZERO(&readfds);
FD_ZERO(&masterfds);
FD_SET(serverSocket,&masterfds);    //add udp serverSocket vao array masterfds
int max_fd=serverSocket;     //=3
struct timeval timeout;        //timeout cho select()
timeout.tv_sec=90;
timeout.tv_usec=0;
int n_select;
int close_fd=0;        //khai bao kiem tra fd state
do  { //-----endless loop---------------
memcpy(&readfds,&masterfds,sizeof(masterfds));  //load masterfds to readfds
printf("chuan bi select \n");
n_select=select(max_fd+1,&readfds,NULL,NULL,NULL);
printf("da thuc hien ham select \n");
if (n_select < 0)
        {
                perror("SELECT");
                exit(0);
        }
        else
        if (n_select == 0)
        {
            printf("Time out\n");
        }
        else
        {    
            i=serverSocket;
             // for (i = 0; i <= max_fd;i++)    //duyet cac file descriptors
               //{
                    if (FD_ISSET(i,&readfds))//neu co file descriptor"ready to read"
                    {
                        //int close_fd = 0;    //kiem tra socket co nen duoc dong sau khi xu ly hay ko?
            struct sockaddr_in clientAddress;
            int clientaddrlen=sizeof(clientAddress);
                //gan i =serverSocket    

//-----------------------Data processing---------------------------------------
             printf("receive HELLO+send ACK bulletin\n");
                printf("Receive data in socket %d\n",i);
                            int nrecv ;
            //nhan mail tu remote client 
                    char mail_temp[100][50];        //danh sach tam
                
            dem++;    //thao tac tren mail list dau tien
            nrecv=recvfrom(i,mail_temp[dem],50,0,(struct sockaddr*)&clientAddress,&clientaddrlen);        //hello_mail
                if(nrecv==-1)
                {
                printf("In socket-received mail %d\n",i);
                perror("RECEIVE");
                close_fd=1;   
                }// end if nrecv_mail
            
        //hien thi chuoi
        printf("mail user tu client gui la: %s\n",mail_temp[dem]);     
//-------------------------------------------------------
            nrecv= recvfrom(i,HEL.hello_id,11,0,(struct sockaddr*)&clientAddress,&clientaddrlen);    //PROBLEM HERE-chua gan default cho hello_id o client
                            if (nrecv == -1)
                            {
                                printf("In socket-receive ID %d\n",i);
                                perror("RECEIVE");
                                close_fd = 1;    //co loi nao close_fd=1 de dong socket
                            }
                           // else
                           // {
        printf("Hello_id received=%s.\n",HEL.hello_id);
                

                if(strcmp(HEL.hello_id,"dientu-K53")==0)    //hello_id :dung-> tra ve 0
                {
                printf("ban tin hop le \n");
                goto moveon;
                }
                
                else
                {
                printf("ban tin khong hop le\n");
                exit(0);
                }
        
                    
        
                
    
                        
        //nhan gia tri hello_len
moveon:                nrecv=recvfrom(i,&HEL.hello_len,4,0,(struct sockaddr*)&clientAddress,&clientaddrlen);
                if(nrecv==-1)
                {
                printf("In socket-received length: %d \n",i);
                perror("RECEIVE");
                //close_fd=1;
                }//end if nrecv_len
        //nhan gia tri hello_detect
                nrecv=recvfrom(i,&HEL.hello_detect,4,0,(struct sockaddr*)&clientAddress,&clientaddrlen);
                
                if(nrecv==-1)
                {
                printf("In socket-received detect: %d \n",i);
                perror("RECEIVE");
                close_fd=1;    //dong socket 
                }
        
        //Save email user vao mang 2 chieu
        char list_mail [100][50];
        //mang 1 chieu 100 phan tu, moi phan tu 50 ki tu-> giong danh sach
               // int count=0;
In_mail:        strcpy(list_mail[dem],mail_temp[dem]);
                //cong luon
                printf("mail vua update vao list la: %s \n",list_mail[dem]);
            int j=1;
            printf("------------------Hien thi danh sach email:---------------\n");
            for(j=1;j<=dem;j++)
            {
            printf(" mail thu %d : %s \n ",j,list_mail[j]);
            }
            printf("-------------------End my list----------------------");    
        //gan gia tri cho truong trang thai ACK.ack_state
            
                if(strcmp(list_mail[dem],mail_temp[dem])==0)    //dung->return 0
                {
                printf("luu email thanh cong \n");
                strcpy(ACK.ack_state,"success");
                printf("ack vua gan la %s \n",ACK.ack_state);
                }
                else
                {
                printf("luu email that bai \n");
                strcpy(ACK.ack_state,"failed");
                }
                //ACK length calculation
        //HEL.hello_len=strlen(HEL.hello_id)+strlen(HEL.mail_user)+sizeof(HEL.hello_detect);
        ACK.ack_len=strlen(ACK.ack_id)+sizeof(ACK.ack_detect)+strlen(ACK.client_mail)+strlen(ACK.ack_state)+4;
                //feedback lai client ban tin ack:

                int nsent;
                nsent=sendto(i,ACK.ack_id,11,0,(struct sockaddr*)&clientAddress,clientaddrlen);        //ack_id
                if(nsent==-1)
                {           printf("In socket-error when sending ack ID %d\n",i);
                                            perror("SEND");
                                            close_fd = 1;
                                }
            
                nsent=sendto(i,&ACK.ack_len,4,0,(struct sockaddr*)&clientAddress,clientaddrlen);        //ack_len
                
                if(nsent==-1)
                {           printf("In socket-error when sending ack len %d\n",i);
                                            perror("SEND");
                                            close_fd = 1;
                                }
                nsent=sendto(i,&ACK.ack_detect,4,0,(struct sockaddr*)&clientAddress,clientaddrlen);    //ack_detect

                if(nsent==-1)
                {           printf("In socket-error when sending ack detect %d\n",i);
                                            perror("SEND");
                                            close_fd = 1;
                                }

                strcpy(ACK.client_mail,mail_temp[dem]);    //ack_mail  -< error
                

                nsent=sendto(i,ACK.client_mail,50,0,(struct sockaddr*)&clientAddress,clientaddrlen);
                if(nsent==-1)
                {           printf("In socket-error when sending back CLIENT MAIL %d\n",i);
                                            perror("SEND");
                                            close_fd = 1;
                                }
                printf("state chuan bi gui di la : %s \n",ACK.ack_state);
                nsent=sendto(i,ACK.ack_state,20,0,(struct sockaddr*)&clientAddress,clientaddrlen);    //ack_state
                if(nsent==-1)
                {           printf("In socket-error when sending ack_state %d\n",i);
                                            perror("SEND");
                                            close_fd = 1;
                                }
                printf("state vua gui di la : %s \n",ACK.ack_state);

                printf("successfully sent ACK bulletin to client\n");
                //goto Round_Check;
                    //int nsent = send(i,message2,strlen(message2),0);
                //end feedback

                                   /* else
                                    {
                                        close_fd = 1;
                                    }*/

            printf("receive BYE bulletin \n");        //PROBLEM HERE?
            nrecv=recvfrom(i,BYE.bye_id,11,0,(struct sockaddr*)&clientAddress,&clientaddrlen);        //bye_id
            if(nrecv==-1)
            {
            printf("received bye_id bulletin failed\n");
            perror("RECEIVE");
            exit(0);
            }
            nrecv=recvfrom(i,&BYE.bye_detect,4,0,(struct sockaddr*)&clientAddress,&clientaddrlen);        //bye_detect
            if(nrecv==-1)
            {
            printf("received bye_id bulletin failed\n");
            perror("RECEIVE");
            exit(0);
            }
            close_fd=1;
            printf("remote client closed its socket\n");
            
            goto close_socket;     //thoat khoi checking FD_ISSET

//-----------------------End of data processing--------------------------------        

 
            }//end if of FD_ISSET
        //}//end for
        }//end of else
    }//end do while
while(1);







}// ------------------end esle of DATA handling--------------------
    //close(close_fd);
close_socket: close(serverSocket);

exit(0);


}//end main

client:

Code:

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

#define UDPPORT 5011

int main(int argc,char *argv[])
{
//tao ban tin
struct hello {
char hello_id[11];//10 ky tu dientu-k53 + 1 ki tu ket thuc
long int hello_len; //32bit
long int hello_detect;
char mail_user[50];    //mail user from client
} HEL;
HEL.hello_detect=0;
strcpy(HEL.hello_id,"dientu-K53");

struct acknowledgement {
char ack_id[11];
long int ack_len;
long int ack_detect;
char client_mail[50];    //tra ve mail user cho client
char ack_state[20];     //trang thai "success" or "failed"
} ACK;
strcpy(ACK.ack_id,"dientu-K53");
ACK.ack_detect=1;

struct bye {
char bye_id[11];
long int bye_detect;
} BYE;
strcpy(BYE.bye_id,"dientu-K53");
BYE.bye_detect=2;


//-------------ket thuc tao ban tin----------------------
int clientSocket=socket(PF_INET,SOCK_DGRAM,0);
struct hostent *he;

int check;    //check return value of socket function

if(clientSocket==-1)
{
perror("error making socket\n");
exit(1);
}

struct sockaddr_in serveraddr, clientaddr;
int serveraddrlen=sizeof(serveraddr);

serveraddr.sin_family=AF_INET;
serveraddr.sin_port=htons(UDPPORT);
serveraddr.sin_addr.s_addr=INADDR_ANY;

he=gethostbyname(argv[1]);

//-----------------------Data processing begin ---------------------
printf("nhap email nguoi gui:\n"); int nsend;
        gets(HEL.mail_user);
//verify the null 
        int dem=strlen(HEL.mail_user); //chieu dai
        //HEL.mail_user[dem]='\0';
        if(HEL.mail_user[dem]=='\0') printf("%d th la ki tu NULL\n",dem);
        
        
    
    //calculate len:
        HEL.hello_len=strlen(HEL.hello_id)+strlen(HEL.mail_user)+sizeof(HEL.hello_detect)+4;
    //mail truoc:
        nsend=sendto(clientSocket,HEL.mail_user,strlen(HEL.mail_user),0,(struct sockaddr *)&serveraddr,serveraddrlen);
        if(nsend==-1)
        {
        printf("send email user error\n");
        perror("SEND");
        exit(0);
        }
        printf("hello_len= %ld \n",HEL.hello_len);
    //send "hello" to server
        
        nsend=sendto(clientSocket,HEL.hello_id,11,0,(struct sockaddr *)&serveraddr,serveraddrlen);    //hello_id
        if(nsend==-1)
        {
        printf("send hello_id error\n");
        perror("SEND");
        exit(0);
        }
        
        
            //PROBLEM HERE-them "&"truoc hello_len do truyen buffer
        nsend=sendto(clientSocket,&HEL.hello_len,4,0,(struct sockaddr *)&serveraddr,serveraddrlen);        //hello_len
        if(nsend==-1)
        {
        printf("send hello_len error\n");
        perror("SEND");
        exit(0);
        }
        nsend=sendto(clientSocket,&HEL.hello_detect,4,0,(struct sockaddr *)&serveraddr,serveraddrlen);        //hello_detect
        if(nsend==-1)
        {
        printf("send hello_detect error\n");
        perror("SEND");
        exit(0);
        }//PROBLEM HERE

        printf("Waiting for server reply\n");
        //goto Round_Check;
    // ket thuc send hello

    //*********************************************************

    //nhan ACK & send BYE, dong socket
    printf("nhan ACK, send BYE,close client's corresponding socket\n");
        int nrecv;
        nrecv=recvfrom(clientSocket,ACK.ack_id,11,0,(struct sockaddr *)&serveraddr,&serveraddrlen);    //ack_id
        if(nrecv==-1)
        {
        printf("error when receiving ack_id \n");
        perror("RECEIVE");
        exit(0);
        }
    //hien thi truong nhan dang ack_id cua client:
        printf("truong nhan dang client= %s \n",ACK.ack_id);

        nrecv=recvfrom(clientSocket,&ACK.ack_len,4,0,(struct sockaddr *)&serveraddr,&serveraddrlen);        //ack_len
        if(nrecv==-1)
        {
        printf("error when receiving ack_len \n");
        perror("RECEIVE");
        exit(0);
        }
        nrecv=recvfrom(clientSocket,&ACK.ack_detect,4,0,(struct sockaddr *)&serveraddr,&serveraddrlen);        //ack_detect
        if(nrecv==-1)
        {
        printf("error when receiving ack_detect \n");
        perror("RECEIVE");
        exit(0);
        }
        nrecv=recvfrom(clientSocket,ACK.client_mail,sizeof(HEL.mail_user),0,(struct sockaddr *)&serveraddr,&serveraddrlen);    //ack_mail
        if(nrecv==-1)
        {
        printf("error when receiving client_mail \n");
        perror("RECEIVE");
        exit(0);
        }
        nrecv=recvfrom(clientSocket,ACK.ack_state,20,0,(struct sockaddr *)&serveraddr,&serveraddrlen);        //ack_state
        if(nrecv==-1)
        {
        printf("error when receiving ack_state \n");
        perror("RECEIVE");
        exit(0);
        }
    //hien thi truong trang thai ack_state:
    //khong can them ki tu NULL do luc dau send mail da co
        printf("luu tru email user tai server: %s \n",ACK.ack_state);
        //goto Round_Check;

    //**********************************Round2********************************

    //send "BYE" back to server

        nsend=sendto(clientSocket,BYE.bye_id,11,0,(struct sockaddr *)&serveraddr,serveraddrlen);        //bye_id
        if(nsend==-1)
        {
        printf("error occurrs when sending bye_id\n");
        perror("SEND");
        exit(0);
        }
        nsend=sendto(clientSocket,&BYE.bye_detect,4,0,(struct sockaddr *)&serveraddr,serveraddrlen);        //bye_detect
        if(nsend==-1)
        {
        printf("error occurrs when sending bye_detect\n");
        perror("SEND");
        exit(0);
        }
        printf("send BYE to server successfully, gonna close socket\n");






//-----------------------Data processing end----------------------


close(clientSocket);
exit(0);





}    //------end of main---------

Probably there is something goes wrong with my select() function. I've tried to fix but they are all helpless.
Looking forward to your advices

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