diff --git a/starboard/nplb/socket_get_interface_address_test.cc b/starboard/nplb/socket_get_interface_address_test.cc
index 3f1c145cd56d..0176c4a167df 100644
--- a/starboard/nplb/socket_get_interface_address_test.cc
+++ b/starboard/nplb/socket_get_interface_address_test.cc
@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+#if SB_API_VERSION < 17
+
 #include "starboard/common/socket.h"
 #include "starboard/nplb/socket_helpers.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -184,3 +186,4 @@ INSTANTIATE_TEST_CASE_P(SbSocketAddressTypes,
 }  // namespace
 }  // namespace nplb
 }  // namespace starboard
+#endif  // SB_API_VERSION < 17
diff --git a/starboard/nplb/socket_get_local_address_test.cc b/starboard/nplb/socket_get_local_address_test.cc
index 38954f93c833..50c867fbee4b 100644
--- a/starboard/nplb/socket_get_local_address_test.cc
+++ b/starboard/nplb/socket_get_local_address_test.cc
@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+#if SB_API_VERSION < 17
+
 #include <utility>
 
 #include "starboard/common/socket.h"
@@ -140,3 +142,5 @@ INSTANTIATE_TEST_CASE_P(
 }  // namespace
 }  // namespace nplb
 }  // namespace starboard
+
+#endif  // SB_API_VERSION < 17
diff --git a/starboard/nplb/socket_helpers.cc b/starboard/nplb/socket_helpers.cc
index 3efccdbd5af9..603efeab8857 100644
--- a/starboard/nplb/socket_helpers.cc
+++ b/starboard/nplb/socket_helpers.cc
@@ -68,35 +68,6 @@ int GetPortNumberForTests() {
 #endif
 }
 
-bool IsUnspecified(const SbSocketAddress* address) {
-  // Look at each piece of memory and make sure too many of them aren't zero.
-  int components = (address->type == kSbSocketAddressTypeIpv4 ? 4 : 16);
-  int zero_count = 0;
-  for (int i = 0; i < components; ++i) {
-    if (address->address[i] == 0) {
-      ++zero_count;
-    }
-  }
-  return components == zero_count;
-}
-
-bool IsLocalhost(const SbSocketAddress* address) {
-  if (address->type == kSbSocketAddressTypeIpv4) {
-    return address->address[0] == 127;
-  }
-
-  if (address->type == kSbSocketAddressTypeIpv6) {
-    bool may_be_localhost = true;
-    for (int i = 0; i < 15; ++i) {
-      may_be_localhost &= (address->address[i] == 0);
-    }
-
-    return (may_be_localhost && address->address[15] == 1);
-  }
-
-  return false;
-}
-
 SbSocket CreateServerTcpSocket(SbSocketAddressType address_type) {
   SbSocket server_socket = SbSocketCreate(address_type, kSbSocketProtocolTcp);
   if (!SbSocketIsValid(server_socket)) {
@@ -146,78 +117,6 @@ SbSocket CreateListeningTcpSocket(SbSocketAddressType address_type, int port) {
   return server_socket;
 }
 
-int Transfer(SbSocket receive_socket,
-             char* out_data,
-             SbSocket send_socket,
-             const char* send_data,
-             int size) {
-  int send_total = 0;
-  int receive_total = 0;
-  while (receive_total < size) {
-    if (send_total < size) {
-      int bytes_sent = SbSocketSendTo(send_socket, send_data + send_total,
-                                      size - send_total, NULL);
-      if (bytes_sent < 0) {
-        if (SbSocketGetLastError(send_socket) != kSbSocketPending) {
-          return -1;
-        }
-        bytes_sent = 0;
-      }
-
-      send_total += bytes_sent;
-    }
-
-    int bytes_received = SbSocketReceiveFrom(
-        receive_socket, out_data + receive_total, size - receive_total, NULL);
-    if (bytes_received < 0) {
-      if (SbSocketGetLastError(receive_socket) != kSbSocketPending) {
-        return -1;
-      }
-      bytes_received = 0;
-    }
-
-    receive_total += bytes_received;
-  }
-
-  return size;
-}
-
-int Transfer(Socket* receive_socket,
-             char* out_data,
-             Socket* send_socket,
-             const char* send_data,
-             int size) {
-  int send_total = 0;
-  int receive_total = 0;
-  while (receive_total < size) {
-    if (send_total < size) {
-      int bytes_sent =
-          send_socket->SendTo(send_data + send_total, size - send_total, NULL);
-      if (bytes_sent < 0) {
-        if (!send_socket->IsPending()) {
-          return -1;
-        }
-        bytes_sent = 0;
-      }
-
-      send_total += bytes_sent;
-    }
-
-    int bytes_received = receive_socket->ReceiveFrom(
-        out_data + receive_total, size - receive_total, NULL);
-    if (bytes_received < 0) {
-      if (!receive_socket->IsPending()) {
-        return -1;
-      }
-      bytes_received = 0;
-    }
-
-    receive_total += bytes_received;
-  }
-
-  return size;
-}
-
 int64_t TimedWait(SbSocketWaiter waiter) {
   int64_t start = CurrentMonotonicTime();
   SbSocketWaiterWait(waiter);
diff --git a/starboard/nplb/socket_helpers.h b/starboard/nplb/socket_helpers.h
index 06e5c4e807aa..783cb68e13dc 100644
--- a/starboard/nplb/socket_helpers.h
+++ b/starboard/nplb/socket_helpers.h
@@ -29,14 +29,6 @@ namespace nplb {
 
 const int64_t kSocketTimeout = 200'000;  // 200ms
 
-// Returns true if the given address is the unspecified address (all zeros),
-// supporting both address types.
-bool IsUnspecified(const SbSocketAddress* address);
-
-// Returns true if the given address is the localhost address, supporting both
-// address types.
-bool IsLocalhost(const SbSocketAddress* address);
-
 // Returns a valid port number that can be bound to for use in nplb tests.
 // This will always return the same port number.
 int GetPortNumberForTests();
@@ -50,19 +42,6 @@ SbSocket CreateBoundTcpSocket(SbSocketAddressType address_type, int port);
 // Creates a TCP/IP socket listening on all interfaces on the given port.
 SbSocket CreateListeningTcpSocket(SbSocketAddressType address_type, int port);
 
-// Transfers data between the two connected local sockets, spinning until |size|
-// has been transferred, or an error occurs.
-int Transfer(SbSocket receive_socket,
-             char* out_data,
-             SbSocket send_socket,
-             const char* send_data,
-             int size);
-int Transfer(Socket* receive_socket,
-             char* out_data,
-             Socket* send_socket,
-             const char* send_data,
-             int size);
-
 // Waits on the given waiter, and returns the elapsed time in microseconds.
 int64_t TimedWait(SbSocketWaiter waiter);