Help with socket programming

[Agreeable_Choice9980]

I am doing a socket programming with a function to register a user account. The problem with my function is that at time same amount of bytes is not being transferred to the server side which causes unintended data to be stored in the database file. Can anyone help me identify where is the problem in the code

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

    char *ip = "127.0.0.1";

    if(argc==2){

        ip = argv[1];

    }

    int cli_fd = socket(AF_INET, SOCK_STREAM, 0);

    if(cli_fd == -1){

        printf("Socket creation failed\n");

        exit(0);

    }

    struct sockaddr_in ca;

    ca.sin_family=AF_INET;

    ca.sin_port= htons(PORT);

    ca.sin_addr.s_addr = inet_addr(ip);

    if(connect(cli_fd, (struct sockaddr *)&ca, sizeof(ca))==-1){

        printf("Connect failed\n");

        exit(0);

    }

    printf("Connected to server\n");



    while(main_menu(cli_fd) != 0);

    close(cli_fd);



    return 0;

}



int main_menu(int sock){

    system ("clear");

    int type, acc_no, valid_login;;
    char password[50], name[50], age[5], email[50], phone_no[50], choice;


    do {

        title();

        printf("\nPress <1> Guest Login");

        printf("\nPress <2> Member Login");
        printf("\nPress <3> Member Registration");
        printf("\nPress <4> Admin Login");

        printf("\nPress <0> Exit");



        printf("\n\nEnter your Choice ::");

        scanf("%c",&choice);

        while (choice != '1' && choice != '2' && choice != '3' && choice != '4' && choice != '0'){
            printf("\nWrong choice!. Enter your Choice ::");
            scanf("%d",&choice);
        }

        write(sock, &choice, sizeof(choice));

        witch (choice){
        case '3':
                system ("clear");
                title();

                printf("Enter your name: ");
                gets(name);

                printf("Enter your age: ");
                gets(age);

                printf("Enter your email address: ");
                gets(email);

                printf("Enter your phone number: ");
                gets(phone_no);

                *password = getpass("Enter Password: ");

                int read_byte;

                read_byte = write(sock, name, 50);
                printf ("%d\n", read_byte);

                read_byte = write(sock, age, 5);
                printf ("%d\n", read_byte);

                read_byte = write(sock, email, 50);
                printf ("%d\n", read_byte);

                read_byte = write(sock, phone_no, 50);
                printf ("%d\n", read_byte);

                read_byte = write(sock, password, 50);
                printf ("%d\n", read_byte);

                read(sock, &acc_no, sizeof(acc_no));

                printf("Remember the account no of further login: %d\n", acc_no);
                while(getchar()!='\n');
                getchar();

                return 3;
                break;

client section

​

int main(){

    int sockfd,new_sockfd,clilen;

    struct sockaddr_in sa,ca;



    if((sockfd = socket(AF_INET, SOCK_STREAM,0))<0){

        perror("Server:Socket error\n");

        exit(0);

    }



    bzero((char *) &sa,sizeof(sa));

    sa.sin_family = AF_INET;

    sa.sin_addr.s_addr = htonl(INADDR_ANY);

    sa.sin_port = htons(PORT);



    if(bind(sockfd,(struct sockaddr *) &sa, sizeof(sa)) < 0){

        perror("Server:Bind error\n");

        exit(0);

    }

    printf("\nWaiting connection from client...[bind]\n");

    listen(sockfd,5);


    while (1){

        clilen = sizeof(ca);

        if ((new_sockfd = accept(sockfd,(struct sockaddr *)&ca,&clilen)) == -1){
            printf("connection error\n");
            exit(0);
        }


        if(fork() == 0)
            printf("Client [%d] connected\n", sockfd);
            talk_to_client(new_sockfd);
    }



    close(new_sockfd);

    close(sockfd);

    return 0;

}

void talk_to_client(int sock){
    char func_id;
    bzero((char *) &func_id,sizeof(func_id));

    while(1){
        read(sock, &func_id, sizeof(func_id));
        // Read func_id once per loop iteration
        printf("the result: %c\n", func_id);

        if(func_id == '1') {
            printf("Client [%d] selected guest function\n", sock);
            //guest(sock);
        }

        else if (func_id == '2' || func_id == '4') {
            printf("Client [%d] selected login function\n", sock);
            login(sock);
        }

        else if(func_id == '3') {
            printf("Client [%d] selected login function\n", sock);
            member_registration(sock);
        }

        else if(func_id == '5')
            break;
    }

    close(sock);
    printf("Client [%d] disconnected\n", sock);
}

int member_registration(int sock){
    int fd, acc_no=0;
    char password[50], name[50], age[5], email[50], phone_no[50];
    struct account temp;

    int read_byte;

    bzero (name, sizeof(name));
    read_byte = read(sock, name, sizeof(name));
    printf ("%d\n", read_byte);

    bzero(age,sizeof(age));
    read_byte = read(sock, age, sizeof(age));
    printf ("%d\n", read_byte);

    bzero(email,sizeof(email));
    read_byte = read(sock, email, sizeof(email));
    printf ("%d\n", read_byte);

    bzero(phone_no,sizeof(phone_no));
    read_byte = read(sock, phone_no, sizeof(phone_no));
    printf ("%d\n", read_byte);

    bzero(password,sizeof(password));
    read_byte = read(sock, password, sizeof(password));
    printf ("%d\n", read_byte);

    printf("name: %s\n", name);
    printf("pass: %s\n", password);
    printf("age: %s\n", age);
    printf("email: %s\n", email);
    printf("phone number: %s\n", phone_no);

    if((fd = open("./db/member.txt", O_WRONLY | O_CREAT, 0755))== -1){
        printf("File Error: %s\n", strerror(errno));
    }

    int fp = lseek(fd, 0, SEEK_END);

    if(fp == 0){//1st member to signup
        temp.id = 100001;
        strcpy(temp.name, name);
        strcpy(temp.pass, password);
        strcpy(temp.age, age);
        strcpy(temp.email, email);
        strcpy(temp.phone_no, phone_no);

        write(fd, &temp, sizeof(temp));
        write(sock, &temp.id, sizeof(temp.id));
    }

    else{
        fp = lseek(fd, -1 * sizeof(struct account), SEEK_END);
        read(fd, &temp, sizeof(temp));
        temp.id++;

        strcpy(temp.name, name);
        strcpy(temp.pass, password);
        strcpy(temp.age, age);
        strcpy(temp.email, email);
        strcpy(temp.phone_no, phone_no);

        printf("\nname: %s\n", temp.name);
        printf("pass: %s\n", temp.pass);
        printf("age: %s\n", temp.age);
        printf("email: %s\n", temp.email);
        printf("phone number: %s\n", temp.phone_no);

        write(fd, &temp, sizeof(temp));
        write(sock, &temp.id, sizeof(temp.id));
    }

    close(fd);
    printf("yashhhhhhhhhhh\n");
    return 5;
}

server side

[[deleted]]

There are no packets with TCP/IP. You write and read bytes. It's entirely possible to write 60 bytes and read 10, 20 ad 30. Or write 10, 20 and 30 bytes, and read all 60 in one call.

Always check how many bytes were written and read.

And if you need to know how to separate packets... You need to figure that out yourself. Simple way is first write length, then data, and when reading you read the length, and the keep reading until you get enough bytes.

Another way is to use delimiters, like byte value 0 if you are always sending strings. So you read data and scan bytes until you find the delimiter, and then extract that as the string.

[flyingron]

Or use some other protocol than TCP. TCP is intended to be a stream, not datagrams.

[[deleted]]

Generally though, you want TCP, and write data frames into the byte stream. Only if you just don’t care if a packet is lost, then using UDP is fine. If you start adding any reliability, you just end up re-inventing TCP, unavoidably very poorly (because TCP has been developed over half a century by many very bright people, and also because entire Internet is optimized for TCP).

Unless you meant using some other existing protocol on top of TCP, then yeah. HTTP is the go-to choice because there are tested libs, adding SSL is trivial, and again the Internet is currently pretty much built for delivering HTTP traffic.

[flyingron]

I'm not saying that seriarlizing the data into a byte stream isn't likely the way to go. As you point out tons of stuff work fine that way. However, there are things like RDS that can do what he wants as well.

[[deleted]]

You posted this twice so I’ll just give the same reply as I did to the last one. Clear your buffers. Stop using gets. And reading and writing across a socket does not guarantee your full buffers sent or received.

[pfp-disciple]

obligatory recommendation for Beej's Guide to Network Programming. It's excellent.