diff --git a/src/DHTConnectionSocksProxyImpl.cc b/src/DHTConnectionSocksProxyImpl.cc
new file mode 100644
index 00000000..f7dd7e7c
--- /dev/null
+++ b/src/DHTConnectionSocksProxyImpl.cc
@@ -0,0 +1,145 @@
+/* <!-- copyright */
+/*
+ * aria2 - The high speed download utility
+ *
+ * Copyright (C) 2006 Tatsuhiro Tsujikawa
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ *
+ * In addition, as a special exception, the copyright holders give
+ * permission to link the code of portions of this program with the
+ * OpenSSL library under certain conditions as described in each
+ * individual source file, and distribute linked combinations
+ * including the two.
+ * You must obey the GNU General Public License in all respects
+ * for all of the code used other than OpenSSL.  If you modify
+ * file(s) with this exception, you may extend this exception to your
+ * version of the file(s), but you are not obligated to do so.  If you
+ * do not wish to do so, delete this exception statement from your
+ * version.  If you delete this exception statement from all source
+ * files in the program, then also delete it here.
+ */
+/* copyright --> */
+#include "DHTConnectionSocksProxyImpl.h"
+
+#include <netinet/in.h>
+#include <cstring>
+
+#include "SocketCore.h"
+#include "a2functional.h"
+#include "SocksProxySocket.h"
+
+namespace aria2 {
+
+DHTConnectionSocksProxyImpl::DHTConnectionSocksProxyImpl(int family)
+    : DHTConnectionImpl(family), family_(family)
+{
+}
+
+DHTConnectionSocksProxyImpl::~DHTConnectionSocksProxyImpl() = default;
+
+bool DHTConnectionSocksProxyImpl::startProxy(const std::string& host,
+                                             uint16_t port,
+                                             const std::string& user,
+                                             const std::string& passwd,
+                                             const std::string& listenAddr,
+                                             uint16_t listenPort)
+{
+  socket_ = make_unique<SocksProxySocket>(family_);
+  socket_->establish(host, port);
+
+  // Authentication negotiation
+  bool res = socket_->authByUserpassOrNone(user, passwd);
+  if (!res) {
+    return false;
+  }
+
+  // UDP associate
+  int i =
+      socket_->startUdpAssociate(listenAddr, listenPort, bndAddr_, bndPort_);
+  if (i != 0) {
+    return false;
+  }
+  return true;
+}
+
+ssize_t DHTConnectionSocksProxyImpl::receiveMessage(unsigned char* data,
+                                                    size_t len,
+                                                    std::string& host,
+                                                    uint16_t& port)
+{
+  Endpoint remoteEndpoint;
+  size_t resLen = len + (family_ == AF_INET ? 10 : 22);
+  std::string buf;
+  buf.resize(resLen);
+  ssize_t length = getSocket()->readDataFrom(&buf[0], resLen, remoteEndpoint);
+  if (length == 0) {
+    return length;
+  }
+
+  // unencapsulate SOCKS5 UDP header if has
+  if (length > (family_ == AF_INET ? 10 : 22) &&
+      buf.substr(0, 3) == std::string("\x00\x00\x00", 3) &&
+      buf[3] == (family_ == AF_INET ? '\x01' : '\x04')) {
+    if (family_ == AF_INET) {
+      char addrBuf[20];
+      inetNtop(AF_INET, &buf[4], addrBuf, 20);
+      host = std::string(addrBuf);
+      port = ntohs(*(reinterpret_cast<uint16_t*>(&buf[8])));
+      memcpy(data, &buf[10], length - 10);
+      return length - 10;
+    }
+    else {
+      char addrBuf[50];
+      inetNtop(AF_INET6, &buf[4], addrBuf, 50);
+      host = std::string(addrBuf);
+      port = ntohs(*(reinterpret_cast<uint16_t*>(&buf[20])));
+      memcpy(data, &buf[22], length - 22);
+      return length - 22;
+    }
+  }
+  else {
+    host = remoteEndpoint.addr;
+    port = remoteEndpoint.port;
+    return length;
+  }
+}
+
+ssize_t DHTConnectionSocksProxyImpl::sendMessage(const unsigned char* data,
+                                                 size_t len,
+                                                 const std::string& host,
+                                                 uint16_t port)
+{
+  std::string buf;
+  if (family_ == AF_INET) {
+    buf.resize(10);
+    buf[3] = '\x01';
+    // host is got from receiveMessage(). And as socket is binded according to
+    // family, host should be the same family as family_. Omit family checking.
+    net::getBinAddr(&buf[4], host);
+    *(reinterpret_cast<uint16_t*>(&buf[8])) = htons(port);
+    buf.append(reinterpret_cast<const char*>(data), len);
+  }
+  else {
+    buf.resize(22);
+    buf[3] = '\x04';
+    net::getBinAddr(&buf[4], host);
+    *(reinterpret_cast<uint16_t*>(&buf[20])) = htons(port);
+    buf.append(reinterpret_cast<const char*>(data), len);
+  }
+  return getSocket()->writeData(&buf[0], buf.length(), bndAddr_, bndPort_);
+}
+
+} // namespace aria2
diff --git a/src/DHTConnectionSocksProxyImpl.h b/src/DHTConnectionSocksProxyImpl.h
new file mode 100644
index 00000000..cbb39dcc
--- /dev/null
+++ b/src/DHTConnectionSocksProxyImpl.h
@@ -0,0 +1,78 @@
+/* <!-- copyright */
+/*
+ * aria2 - The high speed download utility
+ *
+ * Copyright (C) 2006 Tatsuhiro Tsujikawa
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ *
+ * In addition, as a special exception, the copyright holders give
+ * permission to link the code of portions of this program with the
+ * OpenSSL library under certain conditions as described in each
+ * individual source file, and distribute linked combinations
+ * including the two.
+ * You must obey the GNU General Public License in all respects
+ * for all of the code used other than OpenSSL.  If you modify
+ * file(s) with this exception, you may extend this exception to your
+ * version of the file(s), but you are not obligated to do so.  If you
+ * do not wish to do so, delete this exception statement from your
+ * version.  If you delete this exception statement from all source
+ * files in the program, then also delete it here.
+ */
+/* copyright --> */
+#ifndef D_DHT_CONNECTION_SOCKS_PROXY_IMPL_H
+#define D_DHT_CONNECTION_SOCKS_PROXY_IMPL_H
+
+#include <memory>
+
+#include "DHTConnectionImpl.h"
+#include "SocksProxySocket.h"
+
+namespace aria2 {
+
+class SocketCore;
+
+class DHTConnectionSocksProxyImpl : public DHTConnectionImpl {
+private:
+  std::unique_ptr<SocksProxySocket> socket_;
+  int family_;
+  std::string bndAddr_;
+  uint16_t bndPort_;
+
+public:
+  DHTConnectionSocksProxyImpl(int family);
+
+  virtual ~DHTConnectionSocksProxyImpl();
+
+  // Connect to SOCKS5 server to start UDP proxy.
+  // Leave user and passwd empty to indicate no authentication.
+  // Leave listen host and port empty / 0 to indicate no receiving from proxy.
+  // MUST call the method before any receiveMessage/sendMessage.
+  bool startProxy(const std::string& host, uint16_t port,
+                  const std::string& user, const std::string& passwd,
+                  const std::string& listenAddr, uint16_t listenPort);
+
+  virtual ssize_t receiveMessage(unsigned char* data, size_t len,
+                                 std::string& host,
+                                 uint16_t& port) CXX11_OVERRIDE;
+
+  virtual ssize_t sendMessage(const unsigned char* data, size_t len,
+                              const std::string& host,
+                              uint16_t port) CXX11_OVERRIDE;
+};
+
+} // namespace aria2
+
+#endif // D_DHT_CONNECTION_SOCKS_PROXY_IMPL_H
diff --git a/src/DHTSetup.cc b/src/DHTSetup.cc
index d107a53e..02e20f29 100644
--- a/src/DHTSetup.cc
+++ b/src/DHTSetup.cc
@@ -41,6 +41,7 @@
 #include "util.h"
 #include "DHTNode.h"
 #include "DHTConnectionImpl.h"
+#include "DHTConnectionSocksProxyImpl.h"
 #include "DHTRoutingTable.h"
 #include "DHTMessageFactoryImpl.h"
 #include "DHTMessageTracker.h"
@@ -113,7 +114,10 @@ DHTSetup::setup(DownloadEngine* e, int family)
     }
 
     uint16_t port;
-    auto connection = make_unique<DHTConnectionImpl>(family);
+    const std::string& proxyUri = e->getOption()->get(PREF_BT_UDP_SOCKS_PROXY);
+    auto connection = proxyUri.empty()
+                          ? make_unique<DHTConnectionImpl>(family)
+                          : make_unique<DHTConnectionSocksProxyImpl>(family);
     {
       port = e->getBtRegistry()->getUdpPort();
       const std::string& addr = e->getOption()->get(
@@ -139,6 +143,24 @@ DHTSetup::setup(DownloadEngine* e, int family)
     }
     A2_LOG_DEBUG(fmt("Initialized local node ID=%s",
                      util::toHex(localNode->getID(), DHT_ID_LENGTH).c_str()));
+    if (!proxyUri.empty()) {
+      auto c = static_cast<DHTConnectionSocksProxyImpl*>(connection.get());
+      const std::string& user =
+          e->getOption()->get(PREF_BT_UDP_SOCKS_PROXY_USER);
+      const std::string& passwd =
+          e->getOption()->get(PREF_BT_UDP_SOCKS_PROXY_PASSWD);
+      uri::UriStruct us;
+      uri::parse(us, proxyUri);
+      const std::string& host = us.host;
+      uint16_t port = us.port;
+      if (!c->startProxy(host, port, user, passwd, localNode->getIPAddress(),
+                         localNode->getPort())) {
+        throw DL_ABORT_EX("Error occurred while connecting to SOCKS5 relay "
+                          "server for UDP proxy for DHT and UDP trackers");
+      }
+      A2_LOG_DEBUG(fmt("Connected to SOCKS5 relay server %s:%u for UDP proxy",
+                       host.c_str(), port));
+    }
     auto tracker = std::make_shared<DHTMessageTracker>();
     auto routingTable = make_unique<DHTRoutingTable>(localNode);
     auto factory = make_unique<DHTMessageFactoryImpl>(family);
diff --git a/src/FeatureConfig.cc b/src/FeatureConfig.cc
index 2b43c8b1..98e6b115 100644
--- a/src/FeatureConfig.cc
+++ b/src/FeatureConfig.cc
@@ -88,6 +88,9 @@ uint16_t getDefaultPort(const std::string& protocol)
   else if (protocol == "sftp") {
     return 22;
   }
+  else if (protocol == "socks") {
+    return 1080;
+  }
   else {
     return 0;
   }
diff --git a/src/Makefile.am b/src/Makefile.am
index cb6e3b7c..c8d6f4f0 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -231,6 +231,7 @@ SRCS =  \
 	SocketBuffer.cc SocketBuffer.h\
 	SocketCore.cc SocketCore.h\
 	SocketRecvBuffer.cc SocketRecvBuffer.h\
+	SocksProxySocket.cc SocksProxySocket.h\
 	SpeedCalc.cc SpeedCalc.h\
 	StatCalc.h\
 	StreamCheckIntegrityEntry.cc StreamCheckIntegrityEntry.h\
@@ -503,6 +504,7 @@ SRCS += \
 	DHTBucketTree.cc DHTBucketTree.h\
 	DHTConnection.h\
 	DHTConnectionImpl.cc DHTConnectionImpl.h\
+	DHTConnectionSocksProxyImpl.cc DHTConnectionSocksProxyImpl.h\
 	DHTConstants.h\
 	DHTEntryPointNameResolveCommand.cc DHTEntryPointNameResolveCommand.h\
 	DHTFindNodeMessage.cc DHTFindNodeMessage.h\
diff --git a/src/OptionHandlerFactory.cc b/src/OptionHandlerFactory.cc
index 000426b6..b5f25a30 100644
--- a/src/OptionHandlerFactory.cc
+++ b/src/OptionHandlerFactory.cc
@@ -1379,6 +1379,37 @@ std::vector<OptionHandler*> OptionHandlerFactory::createOptionHandlers()
     op->setChangeOptionForReserved(true);
     handlers.push_back(op);
   }
+  {
+    OptionHandler* op(new SocksProxyOptionHandler(
+        PREF_BT_UDP_SOCKS_PROXY, TEXT_BT_UDP_SOCKS_PROXY, NO_DEFAULT_VALUE));
+    op->addTag(TAG_BITTORRENT);
+    op->setInitialOption(true);
+    op->setChangeGlobalOption(true);
+    op->setChangeOptionForReserved(true);
+    handlers.push_back(op);
+  }
+  {
+    OptionHandler* op(new DefaultOptionHandler(PREF_BT_UDP_SOCKS_PROXY_PASSWD,
+                                               TEXT_BT_UDP_SOCKS_PROXY_PASSWD,
+                                               NO_DEFAULT_VALUE));
+    op->addTag(TAG_BITTORRENT);
+    op->setEraseAfterParse(true);
+    op->setInitialOption(true);
+    op->setChangeGlobalOption(true);
+    op->setChangeOptionForReserved(true);
+    handlers.push_back(op);
+  }
+  {
+    OptionHandler* op(new DefaultOptionHandler(PREF_BT_UDP_SOCKS_PROXY_USER,
+                                               TEXT_BT_UDP_SOCKS_PROXY_USER,
+                                               NO_DEFAULT_VALUE));
+    op->addTag(TAG_BITTORRENT);
+    op->setEraseAfterParse(true);
+    op->setInitialOption(true);
+    op->setChangeGlobalOption(true);
+    op->setChangeOptionForReserved(true);
+    handlers.push_back(op);
+  }
   {
     OptionHandler* op(new HttpProxyOptionHandler(PREF_ALL_PROXY, TEXT_ALL_PROXY,
                                                  NO_DEFAULT_VALUE));
diff --git a/src/OptionHandlerImpl.cc b/src/OptionHandlerImpl.cc
index 6214e84b..93c82c7d 100644
--- a/src/OptionHandlerImpl.cc
+++ b/src/OptionHandlerImpl.cc
@@ -529,6 +529,48 @@ std::string HttpProxyOptionHandler::createPossibleValuesString() const
   return "[http://][USER:PASSWORD@]HOST[:PORT]";
 }
 
+SocksProxyOptionHandler::SocksProxyOptionHandler(
+    PrefPtr pref, const char* description, const std::string& defaultValue,
+    char shortName)
+    : AbstractOptionHandler(pref, description, defaultValue,
+                            OptionHandler::REQ_ARG, shortName),
+      proxyUserPref_(option::k2p(std::string(pref->k) + "-user")),
+      proxyPasswdPref_(option::k2p(std::string(pref->k) + "-passwd"))
+{
+}
+
+SocksProxyOptionHandler::~SocksProxyOptionHandler() = default;
+
+void SocksProxyOptionHandler::parseArg(Option& option,
+                                       const std::string& optarg) const
+{
+  if (optarg.empty()) {
+    option.put(pref_, optarg);
+  }
+  else {
+    std::string uri;
+    if (util::startsWith(optarg, "socks://") ||
+        util::startsWith(optarg, "socks5://")) {
+      uri = optarg;
+    }
+    else {
+      uri = "socks://";
+      uri += optarg;
+    }
+    uri::UriStruct us;
+    if (!uri::parse(us, uri)) {
+      throw DL_ABORT_EX(_("unrecognized proxy format"));
+    }
+    us.protocol = "socks";
+    option.put(pref_, uri::construct(us));
+  }
+}
+
+std::string SocksProxyOptionHandler::createPossibleValuesString() const
+{
+  return "[socks[5]://][USER:PASSWORD@]HOST[:PORT]";
+}
+
 LocalFilePathOptionHandler::LocalFilePathOptionHandler(
     PrefPtr pref, const char* description, const std::string& defaultValue,
     bool acceptStdin, char shortName, bool mustExist,
diff --git a/src/OptionHandlerImpl.h b/src/OptionHandlerImpl.h
index 7846b226..7404e3b6 100644
--- a/src/OptionHandlerImpl.h
+++ b/src/OptionHandlerImpl.h
@@ -230,6 +230,20 @@ public:
   virtual std::string createPossibleValuesString() const CXX11_OVERRIDE;
 };
 
+class SocksProxyOptionHandler : public AbstractOptionHandler {
+private:
+  PrefPtr proxyUserPref_;
+  PrefPtr proxyPasswdPref_;
+
+public:
+  SocksProxyOptionHandler(PrefPtr pref, const char* description,
+                          const std::string& defaultValue, char shortName = 0);
+  virtual ~SocksProxyOptionHandler();
+  virtual void parseArg(Option& option,
+                        const std::string& optarg) const CXX11_OVERRIDE;
+  virtual std::string createPossibleValuesString() const CXX11_OVERRIDE;
+};
+
 class LocalFilePathOptionHandler : public AbstractOptionHandler {
 private:
   std::string possibleValuesString_;
diff --git a/src/SocksProxySocket.cc b/src/SocksProxySocket.cc
new file mode 100644
index 00000000..5f4d6270
--- /dev/null
+++ b/src/SocksProxySocket.cc
@@ -0,0 +1,245 @@
+/* <!-- copyright */
+/*
+ * aria2 - The high speed download utility
+ *
+ * Copyright (C) 2006 Tatsuhiro Tsujikawa
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ *
+ * In addition, as a special exception, the copyright holders give
+ * permission to link the code of portions of this program with the
+ * OpenSSL library under certain conditions as described in each
+ * individual source file, and distribute linked combinations
+ * including the two.
+ * You must obey the GNU General Public License in all respects
+ * for all of the code used other than OpenSSL.  If you modify
+ * file(s) with this exception, you may extend this exception to your
+ * version of the file(s), but you are not obligated to do so.  If you
+ * do not wish to do so, delete this exception statement from your
+ * version.  If you delete this exception statement from all source
+ * files in the program, then also delete it here.
+ */
+/* copyright --> */
+#include "SocksProxySocket.h"
+
+#include <netinet/in.h>
+#include <sstream>
+
+#include "SocketCore.h"
+#include "a2functional.h"
+
+namespace {
+const char C_SOCKS_VER = '\x05';
+const char C_AUTH_NONE = '\xff';
+const char C_AUTH_USERPASS_VER = '\x01';
+const char C_AUTH_USERPASS_OK = '\x00';
+const char C_OK = '\x00';
+} // namespace
+
+namespace aria2 {
+
+enum SocksProxyAddrType {
+  SOCKS_ADDR_INET = 1,
+  SOCKS_ADDR_DOMAIN = 3,
+  SOCKS_ADDR_INET6 = 4,
+};
+
+SocksProxySocket::SocksProxySocket(int family) : family_(family) {}
+
+SocksProxySocket::~SocksProxySocket() = default;
+
+void SocksProxySocket::establish(const std::string& host, uint16_t port)
+{
+  socket_ = make_unique<SocketCore>();
+  socket_->establishConnection(host, port);
+  socket_->setBlockingMode();
+}
+
+void SocksProxySocket::establish(std::unique_ptr<SocketCore> socket)
+{
+  socket_ = std::move(socket);
+}
+
+int SocksProxySocket::negotiateAuth(std::vector<SocksProxyAuthMethod> expected)
+{
+  std::stringstream req;
+  req << C_SOCKS_VER;
+  req << static_cast<char>(expected.size());
+  for (auto c : expected) {
+    req << static_cast<char>(c);
+  }
+  socket_->writeData(req.str());
+
+  char res[2];
+  size_t resLen = sizeof(res);
+  socket_->readData(res, resLen);
+  int authMethod = res[1];
+  if (authMethod == C_AUTH_NONE) {
+    socket_->closeConnection();
+    return -1;
+  }
+  return authMethod;
+}
+
+int SocksProxySocket::authByUserpass(const std::string& user,
+                                     const std::string& passwd)
+{
+  std::stringstream req;
+  req << C_AUTH_USERPASS_VER;
+  req << static_cast<char>(user.length()) << user;
+  req << static_cast<char>(passwd.length()) << passwd;
+  socket_->writeData(req.str());
+
+  char res[2];
+  size_t resLen = sizeof(res);
+  socket_->readData(res, resLen);
+  if (res[1] != C_AUTH_USERPASS_OK) {
+    socket_->closeConnection();
+  }
+  return res[1];
+}
+
+bool SocksProxySocket::authByUserpassOrNone(const std::string& user,
+                                            const std::string& passwd)
+{
+  bool noAuth = user.empty() || passwd.empty();
+  if (noAuth) {
+    int authMethod =
+        negotiateAuth(std::vector<SocksProxyAuthMethod>{SOCKS_AUTH_NO_AUTH});
+    if (authMethod < 0) {
+      return false;
+    }
+  }
+  else {
+    int authMethod = negotiateAuth(std::vector<SocksProxyAuthMethod>{
+        SOCKS_AUTH_NO_AUTH, SOCKS_AUTH_USERPASS});
+    if (authMethod < 0) {
+      return false;
+    }
+    if (authMethod == SOCKS_AUTH_USERPASS) {
+      int status = authByUserpass(user, passwd);
+      if (status != 0) {
+        return false;
+      }
+    }
+  }
+  return true;
+}
+
+void SocksProxySocket::sendCmd(SocksProxyCmd cmd, const std::string& dstAddr,
+                               uint16_t dstPort, bool allowEmpty)
+{
+  std::stringstream req;
+  req << C_SOCKS_VER << static_cast<char>(cmd) << '\x00';
+  if (family_ == AF_INET) {
+    if (!allowEmpty || !dstAddr.empty()) {
+      char addrBuf[10];
+      net::getBinAddr(addrBuf, dstAddr);
+      req << static_cast<char>(SOCKS_ADDR_INET) << std::string(addrBuf, 4);
+    }
+    else {
+      req << std::string(4, '\x00');
+    }
+  }
+  else {
+    if (!allowEmpty || !dstAddr.empty()) {
+      char addrBuf[20];
+      net::getBinAddr(addrBuf, dstAddr);
+      req << static_cast<char>(SOCKS_ADDR_INET6) << std::string(addrBuf, 16);
+    }
+    else {
+      req << std::string(16, '\x00');
+    }
+  }
+  if (dstPort) {
+    uint16_t listenPortBuf = htons(dstPort);
+    req << std::string(reinterpret_cast<const char*>(&listenPortBuf), 2);
+  }
+  else {
+    req << std::string(2, '\x00');
+  }
+  socket_->writeData(req.str());
+}
+
+int SocksProxySocket::receiveReply(int& bndFamily, std::string& bndAddr,
+                                   uint16_t& bndPort)
+{
+  char res[5];
+  size_t resLen = sizeof(res);
+  socket_->readData(res, resLen);
+  int rep = res[1];
+  if (rep != C_OK) {
+    socket_->closeConnection();
+    return rep;
+  }
+
+  if (res[3] == SOCKS_ADDR_INET) {
+    char addrBuf[6];
+    addrBuf[0] = res[4];
+    size_t addrLen = sizeof(addrBuf) - 1;
+    socket_->readData(addrBuf + 1, addrLen);
+    char addrStrBuf[20];
+    inetNtop(AF_INET, addrBuf, addrStrBuf, 20);
+    bndFamily = AF_INET;
+    bndAddr = std::string(addrStrBuf);
+    bndPort = ntohs(*reinterpret_cast<uint16_t*>(addrBuf + 4));
+  }
+  else if (res[3] == SOCKS_ADDR_INET6) {
+    char addrBuf[18];
+    addrBuf[0] = res[4];
+    size_t addrLen = sizeof(addrBuf) - 1;
+    socket_->readData(addrBuf + 1, addrLen);
+    char addrStrBuf[50];
+    inetNtop(AF_INET6, addrBuf, addrStrBuf, 50);
+    bndFamily = AF_INET6;
+    bndAddr = std::string(addrStrBuf);
+    bndPort = ntohs(*reinterpret_cast<uint16_t*>(addrBuf + 16));
+  }
+  else if (res[3] == SOCKS_ADDR_DOMAIN) {
+    // 2 more bytes to hold port temporarily.
+    size_t resLen = res[4] + 2;
+    bndAddr = std::string(resLen, '\x00');
+    socket_->readData(&bndAddr[0], resLen);
+    bndFamily = AF_INET + AF_INET6;
+    bndPort = ntohs(*reinterpret_cast<uint16_t*>(&bndAddr[0] + res[4]));
+    bndAddr.resize(res[4]);
+  }
+  else {
+    socket_->closeConnection();
+    return -1;
+  }
+  return rep;
+}
+
+int SocksProxySocket::startUdpAssociate(const std::string& listenAddr,
+                                        uint16_t listenPort,
+                                        std::string& bndAddr, uint16_t& bndPort)
+{
+  sendCmd(SOCKS_CMD_UDP_ASSOCIATE, listenAddr, listenPort, true);
+
+  int bFamily;
+  std::string bAddr;
+  uint16_t bPort;
+  int rep = receiveReply(bFamily, bAddr, bPort);
+  if (rep != C_OK) {
+    return rep;
+  }
+
+  bndAddr = bAddr;
+  bndPort = bPort;
+  return rep;
+}
+
+} // namespace aria2
diff --git a/src/SocksProxySocket.h b/src/SocksProxySocket.h
new file mode 100644
index 00000000..0b603950
--- /dev/null
+++ b/src/SocksProxySocket.h
@@ -0,0 +1,112 @@
+/* <!-- copyright */
+/*
+ * aria2 - The high speed download utility
+ *
+ * Copyright (C) 2006 Tatsuhiro Tsujikawa
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ *
+ * In addition, as a special exception, the copyright holders give
+ * permission to link the code of portions of this program with the
+ * OpenSSL library under certain conditions as described in each
+ * individual source file, and distribute linked combinations
+ * including the two.
+ * You must obey the GNU General Public License in all respects
+ * for all of the code used other than OpenSSL.  If you modify
+ * file(s) with this exception, you may extend this exception to your
+ * version of the file(s), but you are not obligated to do so.  If you
+ * do not wish to do so, delete this exception statement from your
+ * version.  If you delete this exception statement from all source
+ * files in the program, then also delete it here.
+ */
+/* copyright --> */
+#ifndef D_SOCKS_PROXY_SOCKET_H
+#define D_SOCKS_PROXY_SOCKET_H
+
+#include <memory>
+#include <vector>
+#include <string>
+
+namespace aria2 {
+
+class SocketCore;
+
+enum SocksProxyAuthMethod {
+  // No authentication required
+  SOCKS_AUTH_NO_AUTH = 0,
+  // Username/Password authentication
+  SOCKS_AUTH_USERPASS = 2,
+};
+
+// Other than transferring proxy traffic,
+// the class helps to start proxy connections.
+class SocksProxySocket {
+private:
+  int family_;
+  // The socket is not shared because as it is used as some kind of controller,
+  // when it is closed, all related proxy connections are closed.
+  std::unique_ptr<SocketCore> socket_;
+
+  enum SocksProxyCmd {
+    SOCKS_CMD_CONNECT = 1,
+    SOCKS_CMD_BIND = 2,
+    SOCKS_CMD_UDP_ASSOCIATE = 3,
+  };
+
+  // When allowEmtpy is true, allow dst* to be empty.
+  void sendCmd(SocksProxyCmd cmd, const std::string& dstAddr, uint16_t dstPort,
+               bool allowEmpty);
+  // Returns status replied from proxy server. 0 is OK. > 0 with error messages.
+  // < 0 for invalid replies from server.
+  // bndFamily may be AF_INET + AF_INET6 to indicate domain format.
+  int receiveReply(int& bndFamily, std::string& bndAddr, uint16_t& bndPort);
+
+public:
+  SocksProxySocket(int family);
+
+  virtual ~SocksProxySocket();
+
+  // Establish connection to SOCKS port.
+  void establish(const std::string& host, uint16_t port);
+
+  // Customize the TCP socket for SOCKS protocol.
+  // Socket should be blocking to ensure latter steps finished in order.
+  void establish(std::unique_ptr<SocketCore> socket);
+
+  // Negotiate authentication that returns selected auth method in 0-255.
+  // When no auth method is selected, return -1.
+  // Returned auth method SHOULD be in expected but it is not checked.
+  int negotiateAuth(std::vector<SocksProxyAuthMethod> expected);
+
+  // Username/Password authentication.
+  // user and pass should not be empty.
+  // Returns status replied from proxy server. 0 is OK.
+  int authByUserpass(const std::string& user, const std::string& passwd);
+
+  // Helper to negotiate and auth by username/password authentication, or skip
+  // it if not required.
+  // Leave either user or pass empty to force no authentication.
+  bool authByUserpassOrNone(const std::string& user, const std::string& passwd);
+
+  // Create an UDP association to start UDP proxy.
+  // Leave listen host and port empty / 0 to indicate no receiving from proxy.
+  // Returns status replied from proxy server. 0 is OK.
+  int startUdpAssociate(const std::string& listenAddr, uint16_t listenPort,
+                        std::string& bndAddr, uint16_t& bndPort);
+};
+
+} // namespace aria2
+
+#endif // D_SOCKS_PROXY_SOCKET_H
diff --git a/src/option_processing.cc b/src/option_processing.cc
index d95ce753..6a3007dd 100644
--- a/src/option_processing.cc
+++ b/src/option_processing.cc
@@ -263,6 +263,7 @@ error_code::Value option_processing(Option& op, bool standalone,
     overrideWithEnv(*confOption, oparser, PREF_HTTP_PROXY, "http_proxy");
     overrideWithEnv(*confOption, oparser, PREF_HTTPS_PROXY, "https_proxy");
     overrideWithEnv(*confOption, oparser, PREF_FTP_PROXY, "ftp_proxy");
+    overrideWithEnv(*confOption, oparser, PREF_BT_UDP_SOCKS_PROXY, "bt_udp_sokcs_proxy");
     overrideWithEnv(*confOption, oparser, PREF_ALL_PROXY, "all_proxy");
     overrideWithEnv(*confOption, oparser, PREF_NO_PROXY, "no_proxy");
     if (!standalone) {
diff --git a/src/prefs.cc b/src/prefs.cc
index 2591b9f0..2a7c8fd9 100644
--- a/src/prefs.cc
+++ b/src/prefs.cc
@@ -439,6 +439,7 @@ PrefPtr PREF_HTTP_PROXY = makePref("http-proxy");
 PrefPtr PREF_HTTPS_PROXY = makePref("https-proxy");
 PrefPtr PREF_FTP_PROXY = makePref("ftp-proxy");
 PrefPtr PREF_ALL_PROXY = makePref("all-proxy");
+PrefPtr PREF_BT_UDP_SOCKS_PROXY = makePref("bt-udp-socks-proxy");
 // values: comma separated hostname or domain
 PrefPtr PREF_NO_PROXY = makePref("no-proxy");
 // values: get | tunnel
@@ -449,6 +450,8 @@ PrefPtr PREF_HTTPS_PROXY_USER = makePref("https-proxy-user");
 PrefPtr PREF_HTTPS_PROXY_PASSWD = makePref("https-proxy-passwd");
 PrefPtr PREF_FTP_PROXY_USER = makePref("ftp-proxy-user");
 PrefPtr PREF_FTP_PROXY_PASSWD = makePref("ftp-proxy-passwd");
+PrefPtr PREF_BT_UDP_SOCKS_PROXY_USER = makePref("bt-udp-socks-proxy-user");
+PrefPtr PREF_BT_UDP_SOCKS_PROXY_PASSWD = makePref("bt-udp-socks-proxy-passwd");
 PrefPtr PREF_ALL_PROXY_USER = makePref("all-proxy-user");
 PrefPtr PREF_ALL_PROXY_PASSWD = makePref("all-proxy-passwd");
 
diff --git a/src/prefs.h b/src/prefs.h
index 338fd6e6..10de3056 100644
--- a/src/prefs.h
+++ b/src/prefs.h
@@ -390,6 +390,7 @@ extern PrefPtr PREF_NO_WANT_DIGEST_HEADER;
 extern PrefPtr PREF_HTTP_PROXY;
 extern PrefPtr PREF_HTTPS_PROXY;
 extern PrefPtr PREF_FTP_PROXY;
+extern PrefPtr PREF_BT_UDP_SOCKS_PROXY;
 extern PrefPtr PREF_ALL_PROXY;
 // values: comma separated hostname or domain
 extern PrefPtr PREF_NO_PROXY;
@@ -401,6 +402,8 @@ extern PrefPtr PREF_HTTPS_PROXY_USER;
 extern PrefPtr PREF_HTTPS_PROXY_PASSWD;
 extern PrefPtr PREF_FTP_PROXY_USER;
 extern PrefPtr PREF_FTP_PROXY_PASSWD;
+extern PrefPtr PREF_BT_UDP_SOCKS_PROXY_USER;
+extern PrefPtr PREF_BT_UDP_SOCKS_PROXY_PASSWD;
 extern PrefPtr PREF_ALL_PROXY_USER;
 extern PrefPtr PREF_ALL_PROXY_PASSWD;
 
diff --git a/src/usage_text.h b/src/usage_text.h
index 08715436..7f213ab3 100644
--- a/src/usage_text.h
+++ b/src/usage_text.h
@@ -83,6 +83,9 @@
     "                              previously defined proxy, use \"\".\n" \
     "                              See also the --all-proxy option.\n"     \
     "                              This affects all ftp downloads.")
+#define TEXT_BT_UDP_SOCKS_PROXY                                                 \
+  _(" --bt-udp-socks-proxy=PROXY   Use a SOCKS5 proxy server for UDP in BitTorrent.\n"\
+    "                              This affects DHT and connecting UDP trackers in BitTorrent.")
 #define TEXT_ALL_PROXY                                                  \
   _(" --all-proxy=PROXY            Use a proxy server for all protocols. To override\n" \
     "                              a previously defined proxy, use \"\".\n" \
@@ -693,6 +696,10 @@
   _(" --ftp-proxy-user=USER        Set user for --ftp-proxy.")
 #define TEXT_FTP_PROXY_PASSWD                                           \
   _(" --ftp-proxy-passwd=PASSWD    Set password for --ftp-proxy.")
+#define TEXT_BT_UDP_SOCKS_PROXY_USER                                    \
+  _(" --bt-udp-socks-proxy-user=USER Set user for --bt-udp-socks-proxy.")
+#define TEXT_BT_UDP_SOCKS_PROXY_PASSWD                                  \
+  _(" --bt-udp-socks-proxy-passwd=PASSWD Set password for --bt-udp-socks-proxy.")
 #define TEXT_REMOVE_CONTROL_FILE                \
   _(" --remove-control-file[=true|false] Remove control file before download. Using\n" \
     "                              with --allow-overwrite=true, download always\n" \
diff --git a/test/DHTConnectionSocksProxyImplTest.cc b/test/DHTConnectionSocksProxyImplTest.cc
new file mode 100644
index 00000000..3af6b7be
--- /dev/null
+++ b/test/DHTConnectionSocksProxyImplTest.cc
@@ -0,0 +1,82 @@
+#include "DHTConnectionSocksProxyImpl.h"
+
+#include <iostream>
+#include <cppunit/extensions/HelperMacros.h>
+
+#include "Exception.h"
+#include "SocketCore.h"
+#include "A2STR.h"
+
+namespace aria2 {
+
+class DHTConnectionSocksProxyImplTest : public CppUnit::TestFixture {
+
+  CPPUNIT_TEST_SUITE(DHTConnectionSocksProxyImplTest);
+  CPPUNIT_TEST(testWriteAndReadData);
+  CPPUNIT_TEST_SUITE_END();
+
+public:
+  void setUp() {}
+
+  void tearDown() {}
+
+  void testWriteAndReadData();
+};
+
+CPPUNIT_TEST_SUITE_REGISTRATION(DHTConnectionSocksProxyImplTest);
+
+void DHTConnectionSocksProxyImplTest::testWriteAndReadData()
+{
+  try {
+    DHTConnectionSocksProxyImpl con1(AF_INET);
+    uint16_t con1port = 0;
+    CPPUNIT_ASSERT(con1.bind(con1port, "127.0.0.1"));
+
+    DHTConnectionImpl con2(AF_INET);
+    uint16_t con2port = 0;
+    CPPUNIT_ASSERT(con2.bind(con2port, "127.0.0.1"));
+
+    // TODO: Requires a SOCKS5 proxy server for tests
+    return;
+    CPPUNIT_ASSERT(
+        con1.startProxy("localhost", 10801, "", "", "127.0.0.1", con1port));
+
+    std::string message1 = "hello world.";
+    con1.sendMessage(reinterpret_cast<const unsigned char*>(message1.c_str()),
+                     message1.size(), "127.0.0.1", con2port);
+
+    unsigned char readbuffer[100];
+    std::string remoteHost;
+    uint16_t remotePort;
+    {
+      while (!con2.getSocket()->isReadable(0))
+        ;
+      ssize_t rlength = con2.receiveMessage(readbuffer, sizeof(readbuffer),
+                                            remoteHost, remotePort);
+      CPPUNIT_ASSERT_EQUAL((ssize_t)message1.size(), rlength);
+      CPPUNIT_ASSERT_EQUAL(message1,
+                           std::string(&readbuffer[0], &readbuffer[rlength]));
+    }
+
+    std::string message2 = "hello world too.";
+    con2.sendMessage(reinterpret_cast<const unsigned char*>(message2.c_str()),
+                     message2.size(), remoteHost, remotePort);
+
+    {
+      std::string remoteHost;
+      uint16_t remotePort;
+      while (!con1.getSocket()->isReadable(0))
+        ;
+      ssize_t rlength = con1.receiveMessage(readbuffer, sizeof(readbuffer),
+                                            remoteHost, remotePort);
+      CPPUNIT_ASSERT_EQUAL((ssize_t)message2.size(), rlength);
+      CPPUNIT_ASSERT_EQUAL(message2,
+                           std::string(&readbuffer[0], &readbuffer[rlength]));
+    }
+  }
+  catch (Exception& e) {
+    CPPUNIT_FAIL(e.stackTrace());
+  }
+}
+
+} // namespace aria2
diff --git a/test/Makefile.am b/test/Makefile.am
index 49c6211f..cd5b40cb 100644
--- a/test/Makefile.am
+++ b/test/Makefile.am
@@ -171,6 +171,7 @@ aria2c_SOURCES += BtAllowedFastMessageTest.cc\
 	DHTMessageTrackerEntryTest.cc\
 	DHTMessageTrackerTest.cc\
 	DHTConnectionImplTest.cc\
+	DHTConnectionSocksProxyImplTest.cc\
 	DHTPingMessageTest.cc\
 	DHTPingReplyMessageTest.cc\
 	DHTFindNodeMessageTest.cc\