server.cpp

#include <stdio.h>
#include <stdlib.h>
#include <netinet/in.h>
#include <zconf.h>
#include <memory.h>
#include <stdbool.h>
#include <ctype.h>

void error(const char* msg){
    perror(msg);
    exit(0);
}

float stof(const char* s){
    float rez = 0, fact = 1;
    if (*s == '-'){
        s++;
        fact = -1;
    };
    int point_seen;
    for (point_seen = 0; *s; s++){
        if (*s == '.'){
            point_seen = 1;
            continue;
        };
        int d = *s - '0';
        if (d >= 0 && d <= 9){
            if (point_seen) fact /= 10.0f;
            rez = rez * 10.0f + (float)d;
        };
    };
    return rez * fact;
};

float calculator(char calculation[256]) {
    char *token;
    char *val1 = NULL;
    char *val2 = NULL;
    float  v1;
    float  v2;
    bool validCal = true;
    char tempCalculation[256];
    strcpy(tempCalculation,calculation);
    token = strtok(tempCalculation,"+-*//^");
    int c = 0;
    while(token != NULL) {
        c++;
        if(c == 1)
            val1 = token;
        if(c == 2)
            val2 = token;
        token = strtok(NULL,"+-*//^");
    }
    if(c == 2) {
        int i1;
        size_t lenVal1 = strlen(val1);
        for(i1=0; i1<lenVal1 ; i1++) {
            if(!isdigit(val1[i1]))
                break;
        }
        if(i1 != lenVal1)
            validCal = false;

        int i2;
        const int lenVal2 = (const int) (strlen(val2) - 1);
        for(i2 = 0; i2 < lenVal2 ; i2++) {
            if(!isdigit(val2[i2]))
                break;
        }
        if(i2 != lenVal2)
            validCal = false;
        if(validCal){
            char oper = calculation[lenVal1];
            printf("Operator%c\n",oper);
            v1 = stof(val1);
            v2 = stof(val2);
            if(oper == '+') {
                return v1 + v2;
            }
            else if(oper == '-') {
                return v1 - v2;
            }
            else if(oper == '*') {
                return v1 * v2;
            }
            else if(oper == '/') {
                if( v2 == 0){
                    printf("Denominator can't be zero\n");
                    exit(0);
                }
                return v1 / v2;
            }
            else if(oper == '^') {
                printf("Power\n");
            }
            else {
                error("Invalid credential!!!");
            }
        }
        else {
            printf("The values are not numeric!\n");
        }
        return -1;
    }
    else {
        printf("Two operands are required for calculation\n");
        return -1;
    }
};


int main(int argc, char** argv){
    int sockfd, newsockfd;
    char buffer[256];
    socklen_t cli_len;
    struct sockaddr_in serv_addr, cli_addr;
    uint16_t port;
    if(argc < 2){
        error("Argument Error!!!");
    }
    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if(sockfd < 0){
        perror("Unable to create socket!!!");
    }
    bzero((char*)&serv_addr, sizeof(serv_addr));
    port = (uint16_t)atoi(argv[1]);
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_addr.s_addr = INADDR_ANY;
    serv_addr.sin_port = htons(port);
    if(bind(sockfd, (struct sockaddr*)&serv_addr, sizeof(serv_addr)) < 0){
        error("Error in Binding!!!\n");
    }
    listen(sockfd, 5);
    cli_len = sizeof(cli_addr);
    newsockfd = accept(sockfd, (struct sockaddr*)& cli_addr,  &cli_len);
    if(newsockfd < 0){
        error("Error on accepting socket!!!");
    }
    bzero(buffer, 256);
    int n = (int) read(newsockfd, buffer, 255);
    if(n < 0){
        perror("Error to reading socket!!!");
    }
    printf("Here is your entries: %s\n", buffer);
    float result = (float) calculator((char *) buffer);
    printf("Result = %f\n" , result);
    char msg[60];
    char chAns[30]="";
    sprintf(chAns,"%f",result);
    strcat(msg,chAns);
    n = (int) write(newsockfd, msg, strlen(msg));
    if(n < 0){
        error("Error to writing socket!!!");
    }
    close(newsockfd);
    close(sockfd);
    return 0;
}