diff --git a/clang-tools-extra/clangd/index/remote/Client.h b/clang-tools-extra/clangd/index/remote/Client.h
--- a/clang-tools-extra/clangd/index/remote/Client.h
+++ b/clang-tools-extra/clangd/index/remote/Client.h
@@ -22,10 +22,13 @@
 /// described by the remote index. Paths returned by the index will be treated
 /// as relative to this directory.
 ///
-/// This method attempts to resolve the address and establish the connection.
+/// This method attempts to resolve the address and establish the connection by
+/// performing the handshake (sending the data and trying to receive it back).
 ///
-/// \returns nullptr if the address is not resolved during the function call or
-/// if the project was compiled without Remote Index support.
+/// \returns nullptr if one of the following conditions holds:
+/// * Address is not resolved during the function call.
+/// * Handshake was not successful or received data is corrupted.
+/// * Project was compiled without Remote Index support.
 std::unique_ptr<clangd::SymbolIndex> getClient(llvm::StringRef Address,
                                                llvm::StringRef IndexRoot);
 
diff --git a/clang-tools-extra/clangd/index/remote/Client.cpp b/clang-tools-extra/clangd/index/remote/Client.cpp
--- a/clang-tools-extra/clangd/index/remote/Client.cpp
+++ b/clang-tools-extra/clangd/index/remote/Client.cpp
@@ -14,11 +14,14 @@
 #include "marshalling/Marshalling.h"
 #include "support/Logger.h"
 #include "support/Trace.h"
+#include "clang/Basic/LLVM.h"
 #include "clang/Basic/Version.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/Error.h"
 
 #include <chrono>
+#include <cstdint>
+#include <memory>
 
 namespace clang {
 namespace clangd {
@@ -82,6 +85,35 @@
     assert(!ProjectRoot.empty());
   }
 
+  // Returns true if received checksum matches given one.
+  bool handshake(uint32_t Checksum) const {
+    trace::Span Tracer(HandshakeRequest::descriptor()->name());
+    HandshakeRequest RPCRequest;
+    RPCRequest.set_checksum(Checksum);
+    SPAN_ATTACH(Tracer, "Request", RPCRequest.DebugString());
+    grpc::ClientContext Context;
+    Context.AddMetadata("version", clang::getClangToolFullVersion("clangd"));
+    const std::chrono::system_clock::time_point StartTime =
+        std::chrono::system_clock::now();
+    const auto Deadline = StartTime + DeadlineWaitingTime;
+    Context.set_deadline(Deadline);
+    vlog("Sending RPC Request {0}: {1}", HandshakeRequest::descriptor()->name(),
+         RPCRequest.DebugString());
+    HandshakeReply Reply;
+    const grpc::Status Status =
+        Stub.get()->Handshake(&Context, RPCRequest, &Reply);
+    assert(Checksum == Reply.checksum() && "Received checksum should match.");
+    const auto Millis = std::chrono::duration_cast<std::chrono::milliseconds>(
+                            std::chrono::system_clock::now() - StartTime)
+                            .count();
+    const std::string ChecksumMatches =
+        Checksum == Reply.checksum() ? "OK" : "CHECKSUM MISMATCH";
+    vlog("RPC {0} => {1}: {2}ms", HandshakeRequest::descriptor()->name(),
+         ChecksumMatches, Reply.checksum(), Millis);
+    SPAN_ATTACH(Tracer, "Status", Status.ok());
+    return Status.ok() && Checksum == Reply.checksum();
+  }
+
   void lookup(const clangd::LookupRequest &Request,
               llvm::function_ref<void(const clangd::Symbol &)> Callback)
       const override {
@@ -130,8 +162,15 @@
   const auto Channel =
       grpc::CreateChannel(Address.str(), grpc::InsecureChannelCredentials());
   Channel->GetState(true);
-  return std::unique_ptr<clangd::SymbolIndex>(
-      new IndexClient(Channel, ProjectRoot));
+  auto *Idx = new IndexClient(Channel, ProjectRoot);
+  const uint32_t Checksum = 42;
+  const bool OK = Idx->handshake(Checksum);
+  if (!OK) {
+    elog("Handshake did not finish correctly. Breaking the connection to "
+         "remote index.");
+    return nullptr;
+  }
+  return std::unique_ptr<SymbolIndex>(Idx);
 }
 
 } // namespace remote
diff --git a/clang-tools-extra/clangd/index/remote/Index.proto b/clang-tools-extra/clangd/index/remote/Index.proto
--- a/clang-tools-extra/clangd/index/remote/Index.proto
+++ b/clang-tools-extra/clangd/index/remote/Index.proto
@@ -10,6 +10,14 @@
 
 package clang.clangd.remote;
 
+message HandshakeRequest {
+  required uint32 checksum = 1;
+}
+
+message HandshakeReply {
+  required uint32 checksum = 1;
+}
+
 // Common final result for streaming requests.
 message FinalResult { optional bool has_more = 1; }
 
diff --git a/clang-tools-extra/clangd/index/remote/Service.proto b/clang-tools-extra/clangd/index/remote/Service.proto
--- a/clang-tools-extra/clangd/index/remote/Service.proto
+++ b/clang-tools-extra/clangd/index/remote/Service.proto
@@ -15,6 +15,8 @@
 // Semantics of SymbolIndex match clangd::SymbolIndex with all required
 // structures corresponding to their clangd::* counterparts.
 service SymbolIndex {
+  rpc Handshake(HandshakeRequest) returns (HandshakeReply) {}
+
   rpc Lookup(LookupRequest) returns (stream LookupReply) {}
 
   rpc FuzzyFind(FuzzyFindRequest) returns (stream FuzzyFindReply) {}
diff --git a/clang-tools-extra/clangd/index/remote/server/Server.cpp b/clang-tools-extra/clangd/index/remote/server/Server.cpp
--- a/clang-tools-extra/clangd/index/remote/server/Server.cpp
+++ b/clang-tools-extra/clangd/index/remote/server/Server.cpp
@@ -32,6 +32,7 @@
 #include <chrono>
 #include <grpc++/grpc++.h>
 #include <grpc++/health_check_service_interface.h>
+#include <grpcpp/impl/codegen/server_context.h>
 #include <memory>
 #include <thread>
 
@@ -96,6 +97,19 @@
 private:
   using stopwatch = std::chrono::steady_clock;
 
+  grpc::Status Handshake(grpc::ServerContext *Context,
+                         const remote::HandshakeRequest *Request,
+                         HandshakeReply *Reply) override {
+    WithContextValue WithRequestContext(CurrentRequest, Context);
+    logRequest(*Request);
+    trace::Span Tracer("LookupRequest");
+    Reply->set_checksum(Request->checksum());
+    logResponse(*Reply);
+    log("[public] request {0} => OK", HandshakeRequest::descriptor()->name());
+    SPAN_ATTACH(Tracer, "Checksum", Reply->checksum());
+    return grpc::Status::OK;
+  }
+
   grpc::Status Lookup(grpc::ServerContext *Context,
                       const LookupRequest *Request,
                       grpc::ServerWriter<LookupReply> *Reply) override {