transport_tcp.cpp

Go to the documentation of this file.

/*
 * Software License Agreement (BSD License)
 *
 *  Copyright (c) 2008, Willow Garage, Inc.
 *  All rights reserved.
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions
 *  are met:
 *
 *   * Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *   * Redistributions in binary form must reproduce the above
 *     copyright notice, this list of conditions and the following
 *     disclaimer in the documentation and/or other materials provided
 *     with the distribution.
 *   * Neither the name of Willow Garage, Inc. nor the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 *  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 *  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 *  FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 *  COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 *  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 *  BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 *  LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 *  CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 *  LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 *  ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 *  POSSIBILITY OF SUCH DAMAGE.
 */
 
#include "ros/io.h"
#include "ros/transport/transport_tcp.h"
#include "ros/poll_set.h"
#include "ros/header.h"
#include "ros/file_log.h"
#include <ros/assert.h>
#include <sstream>
#include <boost/bind.hpp>
#include <fcntl.h>
#include <errno.h>
#ifndef _WIN32
  #include <sys/socket.h>  // explicit include required for FreeBSD
#endif
namespace ros
{
 
bool TransportTCP::s_use_keepalive_ = true;
bool TransportTCP::s_use_ipv6_ = false;
 
TransportTCP::TransportTCP(PollSet* poll_set, int flags)
: sock_(ROS_INVALID_SOCKET)
, async_connected_(false)
, closed_(false)
, expecting_read_(false)
, expecting_write_(false)
, is_server_(false)
, server_port_(-1)
, local_port_(-1)
, poll_set_(poll_set)
, flags_(flags)
{
 
}
 
TransportTCP::~TransportTCP()
{
  ROS_ASSERT_MSG(sock_ == -1, "TransportTCP socket [%d] was never closed", sock_);
}
 
bool TransportTCP::setSocket(int sock)
{
  sock_ = sock;
  return initializeSocket();
}
 
bool TransportTCP::setNonBlocking()
{
  if (!(flags_ & SYNCHRONOUS))
  {
          int result = set_non_blocking(sock_);
          if ( result != 0 ) {
              ROS_ERROR("setting socket [%d] as non_blocking failed with error [%d]", sock_, result);
      close();
      return false;
    }
  }
 
  return true;
}
 
bool TransportTCP::initializeSocket()
{
  ROS_ASSERT(sock_ != ROS_INVALID_SOCKET);
 
  if (!setNonBlocking())
  {
    return false;
  }
 
  setKeepAlive(s_use_keepalive_, 60, 10, 9);
 
  // connect() will set cached_remote_host_ because it already has the host/port available
  if (cached_remote_host_.empty())
  {
    if (is_server_)
    {
      cached_remote_host_ = "TCPServer Socket";
    }
    else
    {
      std::stringstream ss;
      ss << getClientURI() << " on socket " << sock_;
      cached_remote_host_ = ss.str();
    }
  }
 
  if (local_port_ < 0)
  {
    la_len_ = s_use_ipv6_  ? sizeof(sockaddr_in6) : sizeof(sockaddr_in);
    getsockname(sock_, (sockaddr *)&local_address_, &la_len_);
    switch (local_address_.ss_family)
    {
      case AF_INET:
        local_port_ = ntohs(((sockaddr_in *)&local_address_)->sin_port);
        break;
      case AF_INET6:
        local_port_ = ntohs(((sockaddr_in6 *)&local_address_)->sin6_port);
        break;
    }
  }
 
#ifdef ROSCPP_USE_TCP_NODELAY
  setNoDelay(true);
#endif
 
  ROS_ASSERT(poll_set_ || (flags_ & SYNCHRONOUS));
  if (poll_set_)
  {
    ROS_DEBUG("Adding tcp socket [%d] to pollset", sock_);
    poll_set_->addSocket(sock_, boost::bind(&TransportTCP::socketUpdate, this, boost::placeholders::_1), shared_from_this());
#if defined(POLLRDHUP) // POLLRDHUP is not part of POSIX!
    // This is needed to detect dead connections. #1704
    poll_set_->addEvents(sock_, POLLRDHUP);
#endif
  }
 
  if (!(flags_ & SYNCHRONOUS))
  {
    //enableRead();
  }
 
  return true;
}
 
void TransportTCP::parseHeader(const Header& header)
{
  std::string nodelay;
  if (header.getValue("tcp_nodelay", nodelay) && nodelay == "1")
  {
    ROSCPP_LOG_DEBUG("Setting nodelay on socket [%d]", sock_);
    setNoDelay(true);
  }
}
 
void TransportTCP::setNoDelay(bool nodelay)
{
  int flag = nodelay ? 1 : 0;
  int result = setsockopt(sock_, IPPROTO_TCP, TCP_NODELAY, (char *) &flag, sizeof(int));
  if (result < 0)
  {
    ROS_ERROR("setsockopt failed to set TCP_NODELAY on socket [%d] [%s]", sock_, cached_remote_host_.c_str());
  }
}
 
void TransportTCP::setKeepAlive(bool use, uint32_t idle, uint32_t interval, uint32_t count)
{
  if (use)
  {
    int val = 1;
    if (setsockopt(sock_, SOL_SOCKET, SO_KEEPALIVE, reinterpret_cast<const char*>(&val), sizeof(val)) != 0)
    {
      ROS_DEBUG("setsockopt failed to set SO_KEEPALIVE on socket [%d] [%s]", sock_, cached_remote_host_.c_str());
    }
 
/* cygwin SOL_TCP does not seem to support TCP_KEEPIDLE, TCP_KEEPINTVL, TCP_KEEPCNT */
#if defined(SOL_TCP) && defined(TCP_KEEPIDLE)
    val = idle;
    if (setsockopt(sock_, SOL_TCP, TCP_KEEPIDLE, &val, sizeof(val)) != 0)
    {
      ROS_DEBUG("setsockopt failed to set TCP_KEEPIDLE on socket [%d] [%s]", sock_, cached_remote_host_.c_str());
    }
#else
    (void)idle;
#endif
 
#if defined(SOL_TCP) && defined(TCP_KEEPINTVL)
    val = interval;
    if (setsockopt(sock_, SOL_TCP, TCP_KEEPINTVL, &val, sizeof(val)) != 0)
    {
      ROS_DEBUG("setsockopt failed to set TCP_KEEPINTVL on socket [%d] [%s]", sock_, cached_remote_host_.c_str());
    }
#else
    (void)interval;
#endif
 
#if defined(SOL_TCP) && defined(TCP_KEEPCNT)
    val = count;
    if (setsockopt(sock_, SOL_TCP, TCP_KEEPCNT, &val, sizeof(val)) != 0)
    {
      ROS_DEBUG("setsockopt failed to set TCP_KEEPCNT on socket [%d] [%s]", sock_, cached_remote_host_.c_str());
    }
#else
    (void)count;
#endif
  }
  else
  {
    int val = 0;
    if (setsockopt(sock_, SOL_SOCKET, SO_KEEPALIVE, reinterpret_cast<const char*>(&val), sizeof(val)) != 0)
    {
        ROS_DEBUG("setsockopt failed to set SO_KEEPALIVE on socket [%d] [%s]", sock_, cached_remote_host_.c_str());
    }
  }
}
 
bool TransportTCP::connect(const std::string& host, int port)
{
  if (!isHostAllowed(host))
    return false; // adios amigo
 
  sock_ = socket(s_use_ipv6_ ? AF_INET6 : AF_INET, SOCK_STREAM, 0);
  connected_host_ = host;
  connected_port_ = port;
 
  if (sock_ == ROS_INVALID_SOCKET)
  {
    ROS_ERROR("socket() failed with error [%s]",  last_socket_error_string());
    return false;
  }
 
  setNonBlocking();
 
  sockaddr_storage sas;
  socklen_t sas_len;
 
  in_addr ina;
  in6_addr in6a;
  if (inet_pton(AF_INET, host.c_str(), &ina) == 1)
  {
    sockaddr_in *address = (sockaddr_in*) &sas;
    sas_len = sizeof(sockaddr_in);
    
    la_len_ = sizeof(sockaddr_in);
    address->sin_family = AF_INET;
    address->sin_port = htons(port);
    address->sin_addr.s_addr = ina.s_addr;
  }
  else if (inet_pton(AF_INET6, host.c_str(), &in6a) == 1)
  {
    sockaddr_in6 *address = (sockaddr_in6*) &sas;
    sas_len = sizeof(sockaddr_in6);
    la_len_ = sizeof(sockaddr_in6);
    address->sin6_family = AF_INET6;
    address->sin6_port = htons(port);
    memcpy(address->sin6_addr.s6_addr, in6a.s6_addr, sizeof(in6a.s6_addr));
  }
  else
  {
    struct addrinfo* addr;
    struct addrinfo hints;
    memset(&hints, 0, sizeof(hints));
    hints.ai_family = AF_UNSPEC;
 
    if (getaddrinfo(host.c_str(), NULL, &hints, &addr) != 0)
    {
      close();
      ROS_ERROR("couldn't resolve publisher host [%s]", host.c_str());
      return false;
    }
 
    bool found = false;
    struct addrinfo* it = addr;
    char namebuf[128] = {};
    for (; it; it = it->ai_next)
    {
      if (!s_use_ipv6_ && it->ai_family == AF_INET)
      {
        sockaddr_in *address = (sockaddr_in*) &sas;
        sas_len = sizeof(*address);
        
        memcpy(address, it->ai_addr, it->ai_addrlen);
        address->sin_family = it->ai_family;
        address->sin_port = htons(port);
        
        strncpy(namebuf, inet_ntoa(address->sin_addr), sizeof(namebuf)-1);
        found = true;
        break;
      }
      if (s_use_ipv6_ && it->ai_family == AF_INET6)
      {
        sockaddr_in6 *address = (sockaddr_in6*) &sas;
        sas_len = sizeof(*address);
      
        memcpy(address, it->ai_addr, it->ai_addrlen);
        address->sin6_family = it->ai_family;
        address->sin6_port = htons((u_short) port);
      
        // TODO IPV6: does inet_ntop need other includes for Windows?
        inet_ntop(AF_INET6, (void*)&(address->sin6_addr), namebuf, sizeof(namebuf));
        found = true;
        break;
      }
    }
 
    freeaddrinfo(addr);
 
    if (!found)
    {
      ROS_ERROR("Couldn't resolve an address for [%s]\n", host.c_str());
      return false;
    }
 
    ROSCPP_LOG_DEBUG("Resolved publisher host [%s] to [%s] for socket [%d]", host.c_str(), namebuf, sock_);
  }
 
  int ret = ::connect(sock_, (sockaddr*) &sas, sas_len);
  // windows might need some time to sleep (input from service robotics hack) add this if testing proves it is necessary.
  // ROS_ASSERT((flags_ & SYNCHRONOUS) || ret != 0);
  if (((flags_ & SYNCHRONOUS) && ret != 0) || // synchronous, connect() should return 0
      (!(flags_ & SYNCHRONOUS) && ret != 0 && last_socket_error() != ROS_SOCKETS_ASYNCHRONOUS_CONNECT_RETURN)) 
      // asynchronous, connect() may return 0 or -1. When return -1, WSAGetLastError()=WSAEWOULDBLOCK/errno=EINPROGRESS
  {
    ROSCPP_CONN_LOG_DEBUG("Connect to tcpros publisher [%s:%d] failed with error [%d, %s]", host.c_str(), port, ret, last_socket_error_string());
    close();
 
    return false;
  }
 
  // from daniel stonier:
#ifdef WIN32
  // This is hackish, but windows fails at recv() if its slow to connect (e.g. happens with wireless)
  // recv() needs to check if its connected or not when its asynchronous?
  Sleep(100);
#endif
 
 
  std::stringstream ss;
  ss << host << ":" << port << " on socket " << sock_;
  cached_remote_host_ = ss.str();
 
  if (!initializeSocket())
  {
    return false;
  }
 
  if (flags_ & SYNCHRONOUS)
  {
    ROSCPP_CONN_LOG_DEBUG("connect() succeeded to [%s:%d] on socket [%d]", host.c_str(), port, sock_);
  }
  else
  {
    ROSCPP_CONN_LOG_DEBUG("Async connect() in progress to [%s:%d] on socket [%d]", host.c_str(), port, sock_);
  }
 
  return true;
}
 
bool TransportTCP::listen(int port, int backlog, const AcceptCallback& accept_cb)
{
  is_server_ = true;
  accept_cb_ = accept_cb;
 
  if (s_use_ipv6_)
  {
    sock_ = socket(AF_INET6, SOCK_STREAM, 0);
    sockaddr_in6 *address = (sockaddr_in6 *)&server_address_;
    address->sin6_family = AF_INET6;
    address->sin6_addr = isOnlyLocalhostAllowed() ? 
                         in6addr_loopback : 
                         in6addr_any;
    address->sin6_port = htons(port);
    sa_len_ = sizeof(sockaddr_in6);
  }
  else
  {
    sock_ = socket(AF_INET, SOCK_STREAM, 0);
    sockaddr_in *address = (sockaddr_in *)&server_address_;
    address->sin_family = AF_INET;
    address->sin_addr.s_addr = isOnlyLocalhostAllowed() ? 
                               htonl(INADDR_LOOPBACK) : 
                               INADDR_ANY;
    address->sin_port = htons(port);
    sa_len_ = sizeof(sockaddr_in);
  }
 
  if (sock_ == ROS_INVALID_SOCKET)
  {
    ROS_ERROR("socket() failed with error [%s]", last_socket_error_string());
    return false;
  }
 
 
  if (bind(sock_, (sockaddr *)&server_address_, sa_len_) < 0)
  {
    ROS_ERROR("bind() failed with error [%s]", last_socket_error_string());
    return false;
  }
 
  ::listen(sock_, backlog);
  getsockname(sock_, (sockaddr *)&server_address_, &sa_len_);
 
  switch (server_address_.ss_family)
  {
    case AF_INET:
      server_port_ = ntohs(((sockaddr_in *)&server_address_)->sin_port);
      break;
    case AF_INET6:
      server_port_ = ntohs(((sockaddr_in6 *)&server_address_)->sin6_port);
      break;
  }
 
  if (!initializeSocket())
  {
    return false;
  }
 
  if (!(flags_ & SYNCHRONOUS))
  {
    enableRead();
  }
 
  return true;
}
 
void TransportTCP::close()
{
  Callback disconnect_cb;
 
  if (!closed_)
  {
    {
      boost::recursive_mutex::scoped_lock lock(close_mutex_);
 
      if (!closed_)
      {
        closed_ = true;
 
        ROS_ASSERT(sock_ != ROS_INVALID_SOCKET);
 
        if (poll_set_)
        {
          poll_set_->delSocket(sock_);
        }
 
        ::shutdown(sock_, ROS_SOCKETS_SHUT_RDWR);
        if ( close_socket(sock_) != 0 )
        {
          ROS_ERROR("Error closing socket [%d]: [%s]", sock_, last_socket_error_string());
        } else
        {
          ROSCPP_LOG_DEBUG("TCP socket [%d] closed", sock_);
        }
        sock_ = ROS_INVALID_SOCKET;
 
        disconnect_cb = disconnect_cb_;
 
        disconnect_cb_ = Callback();
        read_cb_ = Callback();
        write_cb_ = Callback();
        accept_cb_ = AcceptCallback();
      }
    }
  }
 
  if (disconnect_cb)
  {
    disconnect_cb(shared_from_this());
  }
}
 
int32_t TransportTCP::read(uint8_t* buffer, uint32_t size)
{
  {
    boost::recursive_mutex::scoped_lock lock(close_mutex_);
 
    // if socket is async and not connected, check if it's conneted
    if (!(flags_ & SYNCHRONOUS) && !async_connected_ && !closed_) {
      int ret, err;
      ret = is_async_connected(sock_, err);
      if (ret == 1) {
        ROSCPP_CONN_LOG_DEBUG("Async socket[%d] is connected", sock_);
        async_connected_ = true;
      } else if (ret == -1) {
        ROSCPP_LOG_DEBUG("Async connect on socket [%d] failed with error [%s]", sock_, socket_error_string(err));
        close();
      } else {
        // socket is connecting
        return 0;
      }
    }
 
    if (closed_)
    {
      ROSCPP_LOG_DEBUG("Tried to read on a closed socket [%d]", sock_);
      return -1;
    }
  }
 
  ROS_ASSERT(size > 0);
 
  // never read more than INT_MAX since this is the maximum we can report back with the current return type
  uint32_t read_size = std::min(size, static_cast<uint32_t>(INT_MAX));
  int num_bytes = ::recv(sock_, reinterpret_cast<char*>(buffer), read_size, 0);
  if (num_bytes < 0)
  {
        if ( !last_socket_error_is_would_block() ) // !WSAWOULDBLOCK / !EAGAIN && !EWOULDBLOCK
    {
      ROSCPP_LOG_DEBUG("recv() on socket [%d] failed with error [%s]", sock_, last_socket_error_string());
      close();
    }
    else
    {
      num_bytes = 0;
    }
  }
  else if (num_bytes == 0)
  {
    ROSCPP_LOG_DEBUG("Socket [%d] received 0/%u bytes, closing", sock_, size);
    close();
    return -1;
  }
 
  return num_bytes;
}
 
int32_t TransportTCP::write(uint8_t* buffer, uint32_t size)
{
  {
    boost::recursive_mutex::scoped_lock lock(close_mutex_);
 
    // if socket is async and not connected, check if it's conneted
    if (!(flags_ & SYNCHRONOUS) && !async_connected_ && !closed_) {
      int ret, err;
      ret = is_async_connected(sock_, err);
      if (ret == 1) {
        ROSCPP_CONN_LOG_DEBUG("Async socket[%d] is connected", sock_);
        async_connected_ = true;
      } else if (ret == -1) {
        ROSCPP_LOG_DEBUG("Async connect on socket [%d] failed with error [%s]", sock_, socket_error_string(err));
        close();
      } else {
        // socket is connecting
        return 0;
      }
    }
 
    if (closed_)
    {
      ROSCPP_LOG_DEBUG("Tried to write on a closed socket [%d]", sock_);
      return -1;
    }
  }
 
  ROS_ASSERT(size > 0);
 
  // never write more than INT_MAX since this is the maximum we can report back with the current return type
  uint32_t writesize = std::min(size, static_cast<uint32_t>(INT_MAX));
  int num_bytes = ::send(sock_, reinterpret_cast<const char*>(buffer), writesize, 0);
  if (num_bytes < 0)
  {
    if ( !last_socket_error_is_would_block() )
    {
      ROSCPP_LOG_DEBUG("send() on socket [%d] failed with error [%s]", sock_, last_socket_error_string());
      close();
    }
    else
    {
      num_bytes = 0;
    }
  }
 
  return num_bytes;
}
 
void TransportTCP::enableRead()
{
  ROS_ASSERT(!(flags_ & SYNCHRONOUS));
 
  {
    boost::recursive_mutex::scoped_lock lock(close_mutex_);
 
    if (closed_)
    {
      return;
    }
  }
 
  if (!expecting_read_)
  {
    poll_set_->addEvents(sock_, POLLIN);
    expecting_read_ = true;
  }
}
 
void TransportTCP::disableRead()
{
  ROS_ASSERT(!(flags_ & SYNCHRONOUS));
 
  {
    boost::recursive_mutex::scoped_lock lock(close_mutex_);
 
    if (closed_)
    {
      return;
    }
  }
 
  if (expecting_read_)
  {
    poll_set_->delEvents(sock_, POLLIN);
    expecting_read_ = false;
  }
}
 
void TransportTCP::enableWrite()
{
  ROS_ASSERT(!(flags_ & SYNCHRONOUS));
 
  {
    boost::recursive_mutex::scoped_lock lock(close_mutex_);
 
    if (closed_)
    {
      return;
    }
  }
 
  if (!expecting_write_)
  {
    poll_set_->addEvents(sock_, POLLOUT);
    expecting_write_ = true;
  }
}
 
void TransportTCP::disableWrite()
{
  ROS_ASSERT(!(flags_ & SYNCHRONOUS));
 
  {
    boost::recursive_mutex::scoped_lock lock(close_mutex_);
 
    if (closed_)
    {
      return;
    }
  }
 
  if (expecting_write_)
  {
    poll_set_->delEvents(sock_, POLLOUT);
    expecting_write_ = false;
  }
}
 
TransportTCPPtr TransportTCP::accept()
{
  ROS_ASSERT(is_server_);
 
  sockaddr client_address;
  socklen_t len = sizeof(client_address);
  int new_sock = ::accept(sock_, (sockaddr *)&client_address, &len);
  if (new_sock >= 0)
  {
    ROSCPP_LOG_DEBUG("Accepted connection on socket [%d], new socket [%d]", sock_, new_sock);
 
    TransportTCPPtr transport(boost::make_shared<TransportTCP>(poll_set_, flags_));
    if (!transport->setSocket(new_sock))
    {
      ROS_ERROR("Failed to set socket on transport for socket %d", new_sock);
    }
 
    return transport;
  }
  else
  {
    ROS_ERROR("accept() on socket [%d] failed with error [%s]", sock_,  last_socket_error_string());
  }
 
  return TransportTCPPtr();
}
 
void TransportTCP::socketUpdate(int events)
{
  {
    boost::recursive_mutex::scoped_lock lock(close_mutex_);
    if (closed_)
    {
      return;
    }
 
    // Handle read events before err/hup/nval, since there may be data left on the wire
    if ((events & POLLIN) && expecting_read_)
    {
      if (is_server_)
      {
        // Should not block here, because poll() said that it's ready
        // for reading
        TransportTCPPtr transport = accept();
        if (transport)
        {
          ROS_ASSERT(accept_cb_);
          accept_cb_(transport);
        }
      }
      else
      {
        if (read_cb_)
        {
          read_cb_(shared_from_this());
        }
      }
    }
 
    if ((events & POLLOUT) && expecting_write_)
    {
      if (write_cb_)
      {
        write_cb_(shared_from_this());
      }
    }
  }
 
  if((events & POLLERR) ||
     (events & POLLHUP) ||
#if defined(POLLRDHUP) // POLLRDHUP is not part of POSIX!
     (events & POLLRDHUP) ||
#endif
     (events & POLLNVAL))
  {
    uint32_t error = -1;
    socklen_t len = sizeof(error);
    if (getsockopt(sock_, SOL_SOCKET, SO_ERROR, reinterpret_cast<char*>(&error), &len) < 0)
    {
      ROSCPP_LOG_DEBUG("getsockopt failed on socket [%d]", sock_);
    }
  #ifdef _MSC_VER
    char err[60];
    strerror_s(err,60,error);
    ROSCPP_LOG_DEBUG("Socket %d closed with (ERR|HUP|NVAL) events %d: %s", sock_, events, err);
  #else
    ROSCPP_LOG_DEBUG("Socket %d closed with (ERR|HUP|NVAL) events %d: %s", sock_, events, strerror(error));
  #endif
 
    close();
  }
}
 
std::string TransportTCP::getTransportInfo()
{
  std::stringstream str;
  str << "TCPROS connection on port " << local_port_ << " to [" << cached_remote_host_ << "]";
  return str.str();
}
 
std::string TransportTCP::getClientURI()
{
  ROS_ASSERT(!is_server_);
 
  sockaddr_storage sas;
  socklen_t sas_len = sizeof(sas);
  getpeername(sock_, (sockaddr *)&sas, &sas_len);
  
  sockaddr_in *sin = (sockaddr_in *)&sas;
  sockaddr_in6 *sin6 = (sockaddr_in6 *)&sas;
 
  char namebuf[128] = {};
  int port;
 
  switch (sas.ss_family)
  {
    case AF_INET:
      port = ntohs(sin->sin_port);
      strncpy(namebuf, inet_ntoa(sin->sin_addr), sizeof(namebuf)-1);
      break;
    case AF_INET6:
      port = ntohs(sin6->sin6_port);
      inet_ntop(AF_INET6, (void*)&(sin6->sin6_addr), namebuf, sizeof(namebuf));
      break;
    default:
      namebuf[0] = 0;
      port = 0;
      break;
  }
 
  std::string ip = namebuf;
  std::stringstream uri;
  uri << ip << ":" << port;
 
  return uri.str();
}
 
} // namespace ros