UDP server/ client exchange bulletin

[markovn]

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:

#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:

#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

[markovn]

P/s I compiled successfully those 2 files above. Generally there is no syntax error (just some insignificant warnings but i guess it's fine) .
I'm using Vmware workstation to create 2 virtual remote machines. Their OS is ubuntu 11.04.
I opened the server first, and client afterward. Client sent all its' messages to server & waiting for server reply. However, the server side seems to be interrupted after implementing "select()" function. This is brief about my symtops.

command to run:
Server: ./server_file_name
Client: ./client_file_name ServerHostname.local

or ./client_file_name Server_IP

I'm glad to receive your help

[Nor]

tcp and udp sockets have many differences. one being the way in which data can be writen and recived.

with tcp you have a large about of data you can send per write.
in udp the maximum amount of data you can send is based on the MTU of the network your using. 1500 bytes is the standard.

your using recvfrom as if it was a tcp connection. I suggest walking the server code line by line in a debugger, untill you see the error.

read this as it will help to
Beej's Guide to Network Programming

[markovn]

Hi bro Nor
Thanks for your advices. Actually i walked through my code line by line previously. I found the problem seems to be caused by "select()" due to the line from 97-99. Here is the quotation

printf("chuan bi select \n");
n_select=select(max_fd+1,&readfds,NULL,NULL,NULL);
printf("da thuc hien ham select \n");

I set 2 "printf" before & after select & received just 1 result from the printf above
printf("chuan bi select \n");

I had already also comprehend the tutorial of Beej as your suggestion above . If you find out any further tips , please tell me.
Thanks again , guy

[Nor]

read the udp socket is with recv or recvfrom, not select.

Someone correct me here,
but doesn't select require a connection to recive data on a socket,
and udp being connectionless, thus will not return untill the timeout is reached?

here is a working example of a client/server echo service that might help you
UDP Client Server Echo Example - GameDev.net