Recv always receive 1 less byte

Question

I'm really tired with this - I tried to fix it for about 5 hours and I still can't semm to find a problem, maybe You guys can.

My problem is that recv at the client side always recv one less byte when I'm sending IP from server. And server is always sending the right ammount of data and right data and IP adress on client side always come without 1 number and it's always the first one so server send:

192.168.0.101

Client receive:

92.168.0.101

What is also important is that client's name is always received without any problems - it only happens with IP adress.

Take a closer look at that:

Server side sending data [2 strings - first is name of client and second is his IP adress]:

j is iterator of list to loop thourght all clients and client variable is the one which is asking for all client's data

std::cout << j->client_name << " ";
int lenght = j->client_name.length()+1 ; //+1 for '\0' byte at the client buffer
std::cout << "Lenght (+1): " << lenght << " ";
lenght = htonl(lenght); //change byte order to network
send(client->client_socket,(char*)&lenght,sizeof(int),0);
std::cout << "I have sent: " <<  send(client->client_socket,j->client_name.c_str(),j->client_name.length(),0) << std::endl;
std::cout << inet_ntoa(j->client_connection.sin_addr) << " "; //showing IP adress
unsigned lenght2 = strlen(inet_ntoa(j->client_connection.sin_addr))+1; //+1 for '\0' byte at the client buffer
std::cout << "Lenght (+1): " << lenght2 << " ";
unsigned realistic_lenght = lenght2;
lenght2 = htonl(lenght2);
send(client->client_socket,(char*)&lenght,sizeof(unsigned),0);
std::cout << "I have sent: " << send(client->client_socket,inet_ntoa(j->client_connection.sin_addr),realistic_lenght,0) << std::endl;

And as I said on server side everything seems to be good and here's code to receive data on client side:

char* data_buffor;
int lenght = 0;
recv(data.client_socket,(char*)&lenght,sizeof(int),0);
lenght = ntohl(lenght);
std::cout << "I have received: " << lenght << std::endl;
data_buffor = new char[lenght];
if (data_buffor != NULL) std::cout << "ALLOCATION WAS SUCCESFULL" << std::endl;
std::cout << "I have received: " << recv(data.client_socket,data_buffor,lenght,0) << std::endl;
data_buffor[lenght-1] = '\0';
temp.client_name = data_buffor; // everything is fine here
delete data_buffor;
data_buffor = NULL;
unsigned lenght2 = 0;
recv(data.client_socket,(char*)&lenght2,sizeof(unsigned),0);
lenght2 = ntohl(lenght2);
std::cout << "I have received: " << lenght2 << std::endl; // I DONT KNOW WHY BUT HERE I GET CRAZY NUMBERS LIKE 3203 and I should get 14 with IP: 192.168.0.101 + one byte for '\0' I think that may be causing all problems but I have no idea how to fix it.
data_buffor = new char[lenght2];
if (data_buffor != NULL) std::cout << "ALLOCATION WAS SUCCESFULL" << std::endl;
std::cout << "I have received " << recv(data.client_socket,data_buffor,lenght2,0) << std::endl;
temp.client_ip_adress = data_buffor;
all_clients.push_back(temp);
delete data_buffor
data_buffor = NULL;

Any help would be highly appreciated.

Answer 1

When the server sends the client name, it is sending the length as the length of the string + 1 to include the terminating NULL character. However, the value returned by std::string::length() does NOT include the terminating NULL, so the server is not actually sending the terminating NULL to the client. When the client then reads the name, it reads the first character of the IP address as the terminating NULL of the name, but you never notice that because the client overwrites that byte in data_buffor with '\0' instead of relying on the server to send the '\0'.