C语言写的一个分布式文件传输服务器

从开源中国里拿来的，学习学习吧，看着还好吧！
Distributed File Sharing System.zip:

else if(argv[1][0] == 's')
{

int opt = TRUE,master_socket , addrlen , new_socket , client_socket[30], activity, i , valread , sd,j,k =9,l = 0,m,max_sd,eff,kk,fee,effd,PORT;
    struct sockaddr_in address;
      
    char buffer[1025],buf[25],prtn[30],ptnumb[30], sln[4],slchar[4],msgdis[100];
    fd_set readfds,connfs;
 
    for (i = 0; i < max_clients; i++) 
    {
        client_socket[i] = 0;
    }
      
    if( (master_socket = socket(AF_INET , SOCK_STREAM , 0)) == 0) 
    {
        perror("socket failed");
        exit(EXIT_FAILURE);
    }
  
    if( setsockopt(master_socket, SOL_SOCKET, SO_REUSEADDR, (char *)&opt, sizeof(opt)) < 0 )
    {
        perror("setsockopt");
        exit(EXIT_FAILURE);
    }
    PORT = atoi(argv[2]);
    address.sin_family = AF_INET;
    address.sin_addr.s_addr = INADDR_ANY;
    address.sin_port = htons( PORT );
    strcpy(masteraddr,"128.205.36.8");
    serverip[0].setvalues(ntohs(address.sin_port),masteraddr,0);//correct here
    szls = 1;  
    if (bind(master_socket, (struct sockaddr *)&address, sizeof(address))<0) 
    {
        perror("bind failed");
        exit(EXIT_FAILURE);
    }
    printf("Listener on port %d \n", PORT);
     
    if (listen(master_socket, 3) < 0)
    {
        perror("listen");
        exit(EXIT_FAILURE);
    }
     
    addrlen = sizeof(address);
    puts("Waiting for connections ...");
    printf("Please enter your option :\nPlease note that you can enter only HELP, CREATOR, DISPLAY AND QUIT for the server\n");
    HELP();
    while(TRUE) 
    {
        FD_ZERO(&readfds);
        FD_SET(master_socket, &readfds);
        FD_SET(STDIN, &readfds);
        max_sd = master_socket;
if(STDIN > max_sd)
{ max_sd = STDIN;
}


        for ( i = 0 ; i < max_clients ; i++) 
        {
            sd = client_socket[i];
             
            if(sd > 0)
                FD_SET( sd , &readfds);
             
            if(sd > max_sd)
                max_sd = sd;
        }
        activity = select( max_sd + 1 , &readfds , NULL , NULL , NULL);
    
        if ((activity < 0) && (errno!=EINTR)) 
        {
            printf("select error");
        }

if(FD_ISSET(STDIN, &readfds)) 
{
fgets(buf,40,stdin);
buf[strlen(buf)-1]='\0';
if(strcmp(buf, "HELP") == 0)
{
HELP();
}
else if(strcmp(buf, "CREATOR") == 0)
{
CREATOR();
}
else if(strcmp(buf, "DISPLAY") == 0)
{
DISPLAY(PORT);
}

else if(strcmp(buf, "QUIT") == 0)
{
int nkk;
printf("Quitting Server\n");
setbuffer();
for (nkk = 0; nkk < max_clients; nkk++) 
        {
         if(client_socket[nkk] > 0)
         {
         if( send(client_socket[nkk], message, strlen(message), 0) != strlen(message) ) 
         {
                perror("send");
         }
         }
        }
  close(master_socket);
  for (nkk = 0; nkk < max_clients; nkk++) 
  {
  sd = client_socket[nkk];
  close(sd);
  }
  exit(0);

}
else
{
printf("Enter a valid option from the list of commands, type HELP to get the List of commands\n");
}
printf("Please enter your option :\n");
}


        if (FD_ISSET(master_socket, &readfds)) {
if ((new_socket = accept(master_socket, (struct sockaddr *)&address, (socklen_t*)&addrlen))<0)
            {
                perror("accept");
                exit(EXIT_FAILURE);
            }
            int n1,n2;char bur[50];
            bzero(bur,256);
            n1 = read(new_socket,bur,255);
            if (n1 < 0) printf("ERROR reading from socket");
            
            printf("New connection,ip is : %s\n",inet_ntoa(address.sin_addr));
            
            n2 = atoi(bur);  
              
            for (i = 0; i < max_clients; i++) 
            {
                if( client_socket[i] == 0 )
                {
                    client_socket[i] = new_socket;
                    serverip[i+1].setvalues(n2,inet_ntoa(address.sin_addr),i+1);
                    printf("----------------------\n");
                    for(eff = 0; eff <= i+1; eff++)
                    {
                    serverip[eff].listm();
                    }
                    if(szls < eff)
                    {
                    szls = eff;
                    }
                    break;
                }

            }
            
            setbuffer();
        for (kk = 0; kk < max_clients; kk++) 
        {
         if(client_socket[kk] > 0)
         {
         if( send(client_socket[kk], message, strlen(message), 0) != strlen(message) ) 
         {
                perror("send");
         }
         }
        }         
        }
         


        for (i = 0; i < max_clients; i++) 
        {
            sd = client_socket[i];
              
            if (FD_ISSET( sd , &readfds)) 
            {
                valread = read( sd , buffer, 1024);
                if (valread == 0)
                {
                    getpeername(sd , (struct sockaddr*)&address , (socklen_t*)&addrlen);
                    
                    for(fee = 0; fee <= szls; fee++)
                    {
                    if(strcmp(inet_ntoa(address.sin_addr), serverip[fee].ipa) == 0)
                    {
                    strcpy(serverip[fee].ipa,"-2");
                    }
                    }
                    close( sd );
                    client_socket[i] = 0;
           
                    setbuffer();
			for (kk = 0; kk < max_clients; kk++) 
			{
			 if(client_socket[kk] > 0)
			 {
			 if( send(client_socket[kk], message, strlen(message), 0) != strlen(message) ) 
			 {
				perror("send");
			 }
			 }
			}   
              }
                        

                else if(strncmp(buffer, "TERMINATE", 9) == 0)
                {   
                    for(effd = 0; effd < szls; effd++)
                    {
                    sprintf(slchar,"%d",serverip[effd].slno);
                    if(buffer[10] == slchar[0])                    
                    {
                    strcpy(serverip[effd].ipa,"-2");
                    sd = client_socket[effd-1];
                    strcpy(msgdis,"Client has been remotely disconnected\n");
                    if(send(client_socket[effd-1], msgdis, strlen(msgdis), 0) != strlen(msgdis) ) 
	            {
		    perror("send");
		    }
                    close(sd);
                    client_socket[effd-1] = 0;
                    break;
                    }
                    }
                    setbuffer();
		    for (kk = 0; kk < max_clients; kk++) 
		    {
	            if(client_socket[kk] > 0)
	            {
		    if( send(client_socket[kk], message, strlen(message), 0) != strlen(message) ) 
	            {
		    perror("send");
		    }
		    }
		    }  
                }
                
                else if(strncmp(buffer, "QUIT", 4) == 0)
                {
                close( sd );
                client_socket[i] = 0;
                strcpy(serverip[i+1].ipa,"-2");
                setbuffer();
		    for (kk = 0; kk < max_clients; kk++) 
		    {
		    if(client_socket[kk] > 0)
		    {
		    if( send(client_socket[kk], message, strlen(message), 0) != strlen(message) ) 
		    {
		    perror("send");
		    }
		    }
		    }
                }
                else
                {
                
                }
            }
        }
    }

}