op_server.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <unistd.h>
#define BUF_SIZE 1024
#define OPSZ 4
void error_handling(char *message);
int calculate(int opnum, int opnd[], char oprator);

int main(int argc, char *argv[]){
    int serv_sock, clnt_sock;
    struct sockaddr_in serv_addr, clnt_addr;
    socklen_t clnt_addr_size = sizeof(clnt_addr);
    char opinfo[BUF_SIZE];
    int result, opnd_cnt, i;
    int recv_cnt, recv_len;
    if(argc != 2){
        printf("Usage : %s <port>\n", argv[0]);
        exit(1);
    }

    serv_sock = socket(PF_INET, SOCK_STREAM, 0);
    if(serv_sock == -1){
        error_handling("socket() error");
    }
    memset(&serv_addr, 0, sizeof(serv_addr));
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    serv_addr.sin_port = htons(atoi(argv[1]));

    if(bind(serv_sock, (struct sockaddr*)&serv_addr, sizeof(serv_addr))== -1){
        error_handling("bind() error");
    }
    if(listen(serv_sock, 5) == -1){
        error_handling("listen() error");
    }

    for(i=0; i<5; i++){
        opnd_cnt = 0;
        clnt_sock = accept(serv_sock, (struct sockaddr*)&clnt_addr, &clnt_addr_size);
        if(clnt_sock == -1){
            error_handling("accept() error");
        }
        read(clnt_sock, &opnd_cnt, 1);

        recv_len = 0;
        while((opnd_cnt*OPSZ+1)>recv_len){
            recv_cnt = read(clnt_sock, &opinfo[recv_len], BUF_SIZE-1);
            recv_len+=recv_cnt;
        }
        result = calculate(opnd_cnt, (int*)opinfo, opinfo[recv_len-1]);
        write(clnt_sock, (char*)&result, sizeof(result));
        close(clnt_sock);
    }
    close(serv_sock);
    return 0;
}

void error_handling(char *message){
    fputs(message, stderr);
    fputc('\n', stderr);
    exit(1);
}

int calculate(int opnum, int opnds[], char op){
    int result=opnds[0], i;
    switch(op){
        case '+':
            for(i=1; i<opnum; i++) result+=opnds[i];
            break;
        case '-':
            for(i=1; i<opnum; i++) result-=opnds[i];
            break;
        case '*':
            for(i=1; i<opnum; i++) result*=opnds[i];
            break;
    }
    return result;
}