Отправка данных по порту

#include <iostream>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <unistd.h>
#include <cstring>
#include <thread>
 
int handlePacket(const char * buf, size_t bufSize)
{
    const char * itByInt = buf;
    int res = 0;
    for (size_t it = 0; it < bufSize; ++it)
    {
        if (::isspace(buf[it]))
        {
            res += atoi(itByInt);
            itByInt = &buf[it] + 1;
        }
    }
 
    res += atoi(itByInt);
    return res;
}
 
void startServer()
{
    int acceptor = ::socket(AF_INET, SOCK_STREAM, 0);
    int client = -1;
    
    if (acceptor == -1)
    {
        std::cerr << "Failed to create server socket\n";
        return;
    }
    
    sockaddr_in addr;
    memset(&addr, 0, sizeof addr);
    addr.sin_family = AF_INET;
    addr.sin_addr.s_addr = INADDR_ANY;
    addr.sin_port = htons(27011);
    
    if (::bind(acceptor, reinterpret_cast<sockaddr *>(&addr), sizeof(addr)) == -1)
    {
        std::cerr << "Failed to bind server socket to host\n";
        return;
    }   
    
    if (::listen(acceptor, 5) == -1)
    {
        std::cerr << "Failed to listen server socket\n";
        return;
    }
    
    if ((client = ::accept(acceptor, NULL, NULL)) == -1)
    {
        std::cerr << "Failed to accept client\n";
        return;
    }
    
    std::cout << "Accept client, start to receive message\n";
    
    const int bufSize = 1024;
    char buf[bufSize] = {};
 
    ssize_t recvSize = ::recv(client, buf, bufSize, 0);
 
    if (recvSize <= 0)
    {
        std::cerr << "Failed to read client socket\n";
        return;
    }
 
    std::cout << "Receive message, start handle\n";
 
    int res = handlePacket(buf, bufSize);
 
    std::cout << "Handle complete, answer: " << res << "\n";
 
    ssize_t sendSize = ::send(client, &res, sizeof res, 0);
 
    if (sendSize <= 0)
    {
        std::cerr << "Failed to send answer to client\n";
        return;
    }
 
    ::shutdown(acceptor, 0x01);
    ::close(acceptor);
    ::close(client);
}
 
int main()
{
    std::thread serverTh(startServer);
    
    hostent * host = NULL;
    const char hostname[] = "localhost";
    
    if ((host = ::gethostbyname(hostname)) == NULL)
    {
        std::cerr << "Can't get host by name: " << hostname << "\n";
        serverTh.detach();
        return 1;
    }
    
    std::cout << "Detected host: " << host->h_addr_list[0] << "\n";
    
    int client = ::socket(AF_INET, SOCK_STREAM, 0);
    
    if (client == -1)
    {
        std::cerr << "Can't create client socket\n";
        serverTh.detach();
        return 1;
    }
    
    sockaddr_in addr;
    memset(&addr, 0, sizeof addr);
    addr.sin_family = AF_INET;
    memcpy(&addr.sin_addr, host->h_addr_list[0], host->h_length);
    addr.sin_port = htons(27011);
    
    std::cout << "Try connect to host\n";
 
    if (::connect(client, reinterpret_cast<sockaddr *>(&addr), sizeof addr) == -1)
    {
        std::cerr << "Can't connect to server host\n";
        serverTh.detach();
        return 1;
    }
    
    std::cout << "Connect successful, try to send data to host\n";
 
    char buf[] = "1 2 3 4";
    
    if (::send(client, buf, sizeof buf, 0) <= 0)
    {
        std::cerr << "Can't send data to host\n";
        serverTh.detach();
        return 1;
    }
 
    int res;
    ssize_t recvSize = ::recv(client, reinterpret_cast<char *>(&res), sizeof res, 0);
    
    if (recvSize <= 0)
    {
        std::cerr << "Can't receive data from host\n";
        serverTh.detach();
        return 1;
    }
    else
    {
        std::cout << "Received answer from host: " << res << "\n";
    }
 
    ::shutdown(client, 0x01);
    ::close(client);
    
    serverTh.join();
}