Programming

        #include <stdlib.h>
        #include <stdio.h>
        #include <unistd.h>
        #include <sys/types.h>
        #include <ctype.h>
        #include <sys/socket.h>
        #include <string.h>
        #include <netinet/in.h>
        #define MAXLENGTH 80
        #define SERVERPORT 1313

        int main(){
            int sockfd;
            struct sockaddr_in server={AF_INET,htons(SERVERPORT),INADDR_ANY};
            int i=0, len;
            char buf[MAXLENGTH],c,d;
            if ((sockfd=socket(AF_INET,SOCK_STREAM,0))==-1){
                perror("socket fallita");
                exit(1);
            }
            if (connect(sockfd, (struct sockaddr *) &server,sizeof server)==-1){
                perror("connect fallita");
                exit(2);
            }
            printf("\nDigita una stringa :");
            while((c=getchar())!='\n' && i<MAXLENGTH){
                if(isalpha(c)!=0){
                        buf[i++]=c;}
                else{
                    i++;
                }
            }
            buf[i]='\0';
            len=strlen(buf);
            printf("\nScrivi + se vuoi tutto maiuscolo e - se vuoi tutto minuscolo:");
            d=getchar();
            if (send(sockfd,&d,1,0)==-1){
                perror("send d fallita");
                exit(4);
            }
            printf("\nInvio la stringa al server...\n");
            if(send(sockfd,buf,len,0)==-1){
                perror("send fallita");
                exit(4);
            }
            if(recv(sockfd,buf,len,0)>0){
                printf("Ho ricevuto la risposta: %s\n",buf);
            }
            else{
                perror("seconda receive fallita");
                exit(3);
            }
            close(sockfd);
            exit(0);
        }

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <ctype.h>
#include <sys/socket.h>
#include <string.h>
#include <signal.h>
#include <netinet/in.h>
#define MAXLENGTH 80
#define SERVERPORT 1313

void minuscolatore (int in,int out){
    char inputline[MAXLENGTH];
    int len,i;
    while((len=recv(in,inputline,MAXLENGTH,0))>0){
        for(i=0;i<len;i++){
            inputline[i]=tolower(inputline[i]);
        }
        send(out,inputline,len,0);
    }
}
void maiuscolatore(int in,int out){
    char inputline[MAXLENGTH];
    int len,i;
    while((len=recv(in,inputline,MAXLENGTH,0))>0){
        for(i=0;i<len;i++){
            inputline[i]=toupper(inputline[i]);
        }
        if (strcmp(inputline,"FINE")==0){
            exit(0);
        }
        send(out,inputline,len,0);
    }
}
int main(){
    int sock,client_len,fd;
    char c;
    struct sockaddr_in client, server = {AF_INET,htons(SERVERPORT),INADDR_ANY};
    if((sock=socket(AF_INET,SOCK_STREAM,0))==-1){
        perror("Socket fallita");
        exit(1);
    }
    if(bind(sock,(struct sockaddr *)&server,sizeof server)==-1){
        perror("Bind fallita");
        exit(2);
    }
    listen(sock,5);
    while(1){
        client_len=sizeof(client);
        if((fd=accept(sock,(struct sockaddr *)&client,&client_len))<0){
            perror("accept fallita");
            exit(3);
        }
        if (recv(fd,&c,1,0)==-1){
            perror("recv server fallita");
            exit(4);
        }
        if (c=='+'){
        switch(fork()){
            case -1:
                perror("Fork fallita");
                exit(4);
            case 0:
                printf("Aperta connessione\n");
                maiuscolatore(fd,fd);
                printf("Chiusa connessione\n");
        }
    }
        else if (c=='-'){
        switch(fork()){
            case -1:
                perror("Fork fallita");
                exit(4);
            case 0:
                printf("Aperta connessione\n");
                minuscolatore(fd,fd);
                printf("Chiusa connessione\n");
        }   
        }
        close(fd);
    }
}