diff --git a/libs/binder/RpcConnection.cpp b/libs/binder/RpcConnection.cpp
index ee5f508..95eba87 100644
--- a/libs/binder/RpcConnection.cpp
+++ b/libs/binder/RpcConnection.cpp
@@ -18,13 +18,7 @@
 
 #include <binder/RpcConnection.h>
 
-#include <arpa/inet.h>
 #include <inttypes.h>
-#include <netdb.h>
-#include <netinet/in.h>
-#include <sys/socket.h>
-#include <sys/types.h>
-#include <sys/un.h>
 #include <unistd.h>
 
 #include <string_view>
@@ -33,6 +27,7 @@
 #include <binder/Stability.h>
 #include <utils/String8.h>
 
+#include "RpcSocketAddress.h"
 #include "RpcState.h"
 #include "RpcWireFormat.h"
 
@@ -40,62 +35,9 @@
 extern "C" pid_t gettid();
 #endif
 
-#ifdef __BIONIC__
-#include <linux/vm_sockets.h>
-#endif
-
 namespace android {
 
-using base::borrowed_fd;
 using base::unique_fd;
-using AddrInfo = std::unique_ptr<addrinfo, decltype(&freeaddrinfo)>;
-
-namespace {
-bool checkSockaddrSize(const char* name, size_t actual, size_t expected) {
-    if (actual >= expected) return true;
-    ALOGW("getSockaddrPort: family is %s but size is %zu < %zu", name, actual, expected);
-    return false;
-}
-
-// Get the port number of |storage| for certain families. Requires storage->sa_family to be
-// set to a known family; otherwise, return nullopt.
-std::optional<unsigned int> getSockaddrPort(const sockaddr* storage, socklen_t len) {
-    switch (storage->sa_family) {
-        case AF_INET: {
-            if (!checkSockaddrSize("INET", len, sizeof(sockaddr_in))) return std::nullopt;
-            auto inetStorage = reinterpret_cast<const sockaddr_in*>(storage);
-            return ntohs(inetStorage->sin_port);
-        }
-        default: {
-            uint16_t family = storage->sa_family;
-            ALOGW("Don't know how to infer port for family %" PRIu16, family);
-            return std::nullopt;
-        }
-    }
-}
-
-std::optional<unsigned int> getSocketPort(borrowed_fd socketfd,
-                                          const RpcConnection::SocketAddress& socketAddress) {
-    sockaddr_storage storage{};
-    socklen_t len = sizeof(storage);
-    auto storagePtr = reinterpret_cast<sockaddr*>(&storage);
-    if (0 != getsockname(socketfd.get(), storagePtr, &len)) {
-        int savedErrno = errno;
-        ALOGE("Could not getsockname at %s: %s", socketAddress.toString().c_str(),
-              strerror(savedErrno));
-        return std::nullopt;
-    }
-
-    // getsockname does not fill in family, but getSockaddrPort() needs it.
-    if (storage.ss_family == AF_UNSPEC) {
-        storage.ss_family = socketAddress.addr()->sa_family;
-    }
-    return getSockaddrPort(storagePtr, len);
-}
-
-} // namespace
-
-RpcConnection::SocketAddress::~SocketAddress() {}
 
 RpcConnection::RpcConnection() {
     LOG_RPC_DETAIL("RpcConnection created %p", this);
@@ -114,134 +56,20 @@
     return sp<RpcConnection>::make();
 }
 
-class UnixSocketAddress : public RpcConnection::SocketAddress {
-public:
-    explicit UnixSocketAddress(const char* path) : mAddr({.sun_family = AF_UNIX}) {
-        unsigned int pathLen = strlen(path) + 1;
-        LOG_ALWAYS_FATAL_IF(pathLen > sizeof(mAddr.sun_path), "Socket path is too long: %u %s",
-                            pathLen, path);
-        memcpy(mAddr.sun_path, path, pathLen);
-    }
-    virtual ~UnixSocketAddress() {}
-    std::string toString() const override {
-        return String8::format("path '%.*s'", static_cast<int>(sizeof(mAddr.sun_path)),
-                               mAddr.sun_path)
-                .c_str();
-    }
-    const sockaddr* addr() const override { return reinterpret_cast<const sockaddr*>(&mAddr); }
-    size_t addrSize() const override { return sizeof(mAddr); }
-
-private:
-    sockaddr_un mAddr;
-};
-
-bool RpcConnection::setupUnixDomainServer(const char* path) {
-    return setupSocketServer(UnixSocketAddress(path));
-}
-
 bool RpcConnection::setupUnixDomainClient(const char* path) {
     return setupSocketClient(UnixSocketAddress(path));
 }
 
 #ifdef __BIONIC__
 
-class VsockSocketAddress : public RpcConnection::SocketAddress {
-public:
-    VsockSocketAddress(unsigned int cid, unsigned int port)
-          : mAddr({
-                    .svm_family = AF_VSOCK,
-                    .svm_port = port,
-                    .svm_cid = cid,
-            }) {}
-    virtual ~VsockSocketAddress() {}
-    std::string toString() const override {
-        return String8::format("cid %u port %u", mAddr.svm_cid, mAddr.svm_port).c_str();
-    }
-    const sockaddr* addr() const override { return reinterpret_cast<const sockaddr*>(&mAddr); }
-    size_t addrSize() const override { return sizeof(mAddr); }
-
-private:
-    sockaddr_vm mAddr;
-};
-
-bool RpcConnection::setupVsockServer(unsigned int port) {
-    // realizing value w/ this type at compile time to avoid ubsan abort
-    constexpr unsigned int kAnyCid = VMADDR_CID_ANY;
-
-    return setupSocketServer(VsockSocketAddress(kAnyCid, port));
-}
-
 bool RpcConnection::setupVsockClient(unsigned int cid, unsigned int port) {
     return setupSocketClient(VsockSocketAddress(cid, port));
 }
 
 #endif // __BIONIC__
 
-class InetSocketAddress : public RpcConnection::SocketAddress {
-public:
-    InetSocketAddress(const sockaddr* sockAddr, size_t size, const char* addr, unsigned int port)
-          : mSockAddr(sockAddr), mSize(size), mAddr(addr), mPort(port) {}
-    [[nodiscard]] std::string toString() const override {
-        return String8::format("%s:%u", mAddr, mPort).c_str();
-    }
-    [[nodiscard]] const sockaddr* addr() const override { return mSockAddr; }
-    [[nodiscard]] size_t addrSize() const override { return mSize; }
-
-private:
-    const sockaddr* mSockAddr;
-    size_t mSize;
-    const char* mAddr;
-    unsigned int mPort;
-};
-
-AddrInfo GetAddrInfo(const char* addr, unsigned int port) {
-    addrinfo hint{
-            .ai_flags = 0,
-            .ai_family = AF_UNSPEC,
-            .ai_socktype = SOCK_STREAM,
-            .ai_protocol = 0,
-    };
-    addrinfo* aiStart = nullptr;
-    if (int rc = getaddrinfo(addr, std::to_string(port).data(), &hint, &aiStart); 0 != rc) {
-        ALOGE("Unable to resolve %s:%u: %s", addr, port, gai_strerror(rc));
-        return AddrInfo(nullptr, nullptr);
-    }
-    if (aiStart == nullptr) {
-        ALOGE("Unable to resolve %s:%u: getaddrinfo returns null", addr, port);
-        return AddrInfo(nullptr, nullptr);
-    }
-    return AddrInfo(aiStart, &freeaddrinfo);
-}
-
-bool RpcConnection::setupInetServer(unsigned int port, unsigned int* assignedPort) {
-    const char* kAddr = "127.0.0.1";
-
-    if (assignedPort != nullptr) *assignedPort = 0;
-    auto aiStart = GetAddrInfo(kAddr, port);
-    if (aiStart == nullptr) return false;
-    for (auto ai = aiStart.get(); ai != nullptr; ai = ai->ai_next) {
-        InetSocketAddress socketAddress(ai->ai_addr, ai->ai_addrlen, kAddr, port);
-        if (!setupSocketServer(socketAddress)) {
-            continue;
-        }
-        auto realPort = getSocketPort(mServer.get(), socketAddress);
-        LOG_ALWAYS_FATAL_IF(!realPort.has_value(), "Unable to get port number after setting up %s",
-                            socketAddress.toString().c_str());
-        LOG_ALWAYS_FATAL_IF(port != 0 && *realPort != port,
-                            "Requesting inet server on %s but it is set up on %u.",
-                            socketAddress.toString().c_str(), *realPort);
-        if (assignedPort != nullptr) {
-            *assignedPort = *realPort;
-        }
-        return true;
-    }
-    ALOGE("None of the socket address resolved for %s:%u can be set up as inet server.", kAddr,
-          port);
-    return false;
-}
-
 bool RpcConnection::setupInetClient(const char* addr, unsigned int port) {
-    auto aiStart = GetAddrInfo(addr, port);
+    auto aiStart = InetSocketAddress::getAddrInfo(addr, port);
     if (aiStart == nullptr) return false;
     for (auto ai = aiStart.get(); ai != nullptr; ai = ai->ai_next) {
         InetSocketAddress socketAddress(ai->ai_addr, ai->ai_addrlen, addr, port);
@@ -287,23 +115,28 @@
     return state()->sendDecStrong(socket.fd(), address);
 }
 
-void RpcConnection::join() {
-    // TODO(b/185167543): do this dynamically, instead of from a static number
-    // of threads
-    unique_fd clientFd(
-            TEMP_FAILURE_RETRY(accept4(mServer.get(), nullptr, 0 /*length*/, SOCK_CLOEXEC)));
-    if (clientFd < 0) {
-        // If this log becomes confusing, should save more state from setupUnixDomainServer
-        // in order to output here.
-        ALOGE("Could not accept4 socket: %s", strerror(errno));
-        return;
+status_t RpcConnection::readId() {
+    {
+        std::lock_guard<std::mutex> _l(mSocketMutex);
+        LOG_ALWAYS_FATAL_IF(mForServer != nullptr, "Can only update ID for client.");
     }
 
-    LOG_RPC_DETAIL("accept4 on fd %d yields fd %d", mServer.get(), clientFd.get());
+    int32_t id;
 
+    ExclusiveSocket socket(sp<RpcConnection>::fromExisting(this), SocketUse::CLIENT);
+    status_t status =
+            state()->getConnectionId(socket.fd(), sp<RpcConnection>::fromExisting(this), &id);
+    if (status != OK) return status;
+
+    LOG_RPC_DETAIL("RpcConnection %p has id %d", this, id);
+    mId = id;
+    return OK;
+}
+
+void RpcConnection::join(unique_fd client) {
     // must be registered to allow arbitrary client code executing commands to
     // be able to do nested calls (we can't only read from it)
-    sp<ConnectionSocket> socket = assignServerToThisThread(std::move(clientFd));
+    sp<ConnectionSocket> socket = assignServerToThisThread(std::move(client));
 
     while (true) {
         status_t error =
@@ -319,41 +152,11 @@
                         "bad state: socket object guaranteed to be in list");
 }
 
-void RpcConnection::setForServer(const wp<RpcServer>& server) {
-    mForServer = server;
-}
-
 wp<RpcServer> RpcConnection::server() {
     return mForServer;
 }
 
-bool RpcConnection::setupSocketServer(const SocketAddress& addr) {
-    LOG_ALWAYS_FATAL_IF(mServer.get() != -1, "Each RpcConnection can only have one server.");
-
-    unique_fd serverFd(
-            TEMP_FAILURE_RETRY(socket(addr.addr()->sa_family, SOCK_STREAM | SOCK_CLOEXEC, 0)));
-    if (serverFd == -1) {
-        ALOGE("Could not create socket: %s", strerror(errno));
-        return false;
-    }
-
-    if (0 != TEMP_FAILURE_RETRY(bind(serverFd.get(), addr.addr(), addr.addrSize()))) {
-        int savedErrno = errno;
-        ALOGE("Could not bind socket at %s: %s", addr.toString().c_str(), strerror(savedErrno));
-        return false;
-    }
-
-    if (0 != TEMP_FAILURE_RETRY(listen(serverFd.get(), 1 /*backlog*/))) {
-        int savedErrno = errno;
-        ALOGE("Could not listen socket at %s: %s", addr.toString().c_str(), strerror(savedErrno));
-        return false;
-    }
-
-    mServer = std::move(serverFd);
-    return true;
-}
-
-bool RpcConnection::setupSocketClient(const SocketAddress& addr) {
+bool RpcConnection::setupSocketClient(const RpcSocketAddress& addr) {
     {
         std::lock_guard<std::mutex> _l(mSocketMutex);
         LOG_ALWAYS_FATAL_IF(mClients.size() != 0,
@@ -373,6 +176,12 @@
         return false;
     }
 
+    if (status_t status = readId(); status != OK) {
+        ALOGE("Could not get connection id after initial connection to %s; %s",
+              addr.toString().c_str(), statusToString(status).c_str());
+        return false;
+    }
+
     // we've already setup one client
     for (size_t i = 0; i + 1 < numThreadsAvailable; i++) {
         // TODO(b/185167543): avoid race w/ accept4 not being called on server
@@ -385,7 +194,7 @@
     return true;
 }
 
-bool RpcConnection::setupOneSocketClient(const SocketAddress& addr) {
+bool RpcConnection::setupOneSocketClient(const RpcSocketAddress& addr) {
     unique_fd serverFd(
             TEMP_FAILURE_RETRY(socket(addr.addr()->sa_family, SOCK_STREAM | SOCK_CLOEXEC, 0)));
     if (serverFd == -1) {
@@ -406,14 +215,19 @@
     return true;
 }
 
-void RpcConnection::addClient(unique_fd&& fd) {
+void RpcConnection::addClient(unique_fd fd) {
     std::lock_guard<std::mutex> _l(mSocketMutex);
     sp<ConnectionSocket> connection = sp<ConnectionSocket>::make();
     connection->fd = std::move(fd);
     mClients.push_back(connection);
 }
 
-sp<RpcConnection::ConnectionSocket> RpcConnection::assignServerToThisThread(unique_fd&& fd) {
+void RpcConnection::setForServer(const wp<RpcServer>& server, int32_t connectionId) {
+    mId = connectionId;
+    mForServer = server;
+}
+
+sp<RpcConnection::ConnectionSocket> RpcConnection::assignServerToThisThread(unique_fd fd) {
     std::lock_guard<std::mutex> _l(mSocketMutex);
     sp<ConnectionSocket> connection = sp<ConnectionSocket>::make();
     connection->fd = std::move(fd);
diff --git a/libs/binder/RpcServer.cpp b/libs/binder/RpcServer.cpp
index 8f2805f..5f024ca 100644
--- a/libs/binder/RpcServer.cpp
+++ b/libs/binder/RpcServer.cpp
@@ -27,10 +27,13 @@
 #include <log/log.h>
 #include "RpcState.h"
 
+#include "RpcSocketAddress.h"
 #include "RpcWireFormat.h"
 
 namespace android {
 
+using base::unique_fd;
+
 RpcServer::RpcServer() {}
 RpcServer::~RpcServer() {}
 
@@ -42,14 +45,63 @@
     mAgreedExperimental = true;
 }
 
+bool RpcServer::setupUnixDomainServer(const char* path) {
+    return setupSocketServer(UnixSocketAddress(path));
+}
+
+#ifdef __BIONIC__
+
+bool RpcServer::setupVsockServer(unsigned int port) {
+    // realizing value w/ this type at compile time to avoid ubsan abort
+    constexpr unsigned int kAnyCid = VMADDR_CID_ANY;
+
+    return setupSocketServer(VsockSocketAddress(kAnyCid, port));
+}
+
+#endif // __BIONIC__
+
+bool RpcServer::setupInetServer(unsigned int port, unsigned int* assignedPort) {
+    const char* kAddr = "127.0.0.1";
+
+    if (assignedPort != nullptr) *assignedPort = 0;
+    auto aiStart = InetSocketAddress::getAddrInfo(kAddr, port);
+    if (aiStart == nullptr) return false;
+    for (auto ai = aiStart.get(); ai != nullptr; ai = ai->ai_next) {
+        InetSocketAddress socketAddress(ai->ai_addr, ai->ai_addrlen, kAddr, port);
+        if (!setupSocketServer(socketAddress)) {
+            continue;
+        }
+
+        LOG_ALWAYS_FATAL_IF(socketAddress.addr()->sa_family != AF_INET, "expecting inet");
+        sockaddr_in addr{};
+        socklen_t len = sizeof(addr);
+        if (0 != getsockname(mServer.get(), reinterpret_cast<sockaddr*>(&addr), &len)) {
+            int savedErrno = errno;
+            ALOGE("Could not getsockname at %s: %s", socketAddress.toString().c_str(),
+                  strerror(savedErrno));
+            return false;
+        }
+        LOG_ALWAYS_FATAL_IF(len != sizeof(addr), "Wrong socket type: len %zu vs len %zu",
+                            static_cast<size_t>(len), sizeof(addr));
+        unsigned int realPort = ntohs(addr.sin_port);
+        LOG_ALWAYS_FATAL_IF(port != 0 && realPort != port,
+                            "Requesting inet server on %s but it is set up on %u.",
+                            socketAddress.toString().c_str(), realPort);
+
+        if (assignedPort != nullptr) {
+            *assignedPort = realPort;
+        }
+
+        return true;
+    }
+    ALOGE("None of the socket address resolved for %s:%u can be set up as inet server.", kAddr,
+          port);
+    return false;
+}
+
 void RpcServer::setMaxThreads(size_t threads) {
     LOG_ALWAYS_FATAL_IF(threads <= 0, "RpcServer is useless without threads");
-    {
-        // this lock should only ever be needed in the error case
-        std::lock_guard<std::mutex> _l(mLock);
-        LOG_ALWAYS_FATAL_IF(mConnections.size() > 0,
-                            "Must specify max threads before creating a connection");
-    }
+    LOG_ALWAYS_FATAL_IF(mStarted, "must be called before started");
     mMaxThreads = threads;
 }
 
@@ -67,30 +119,36 @@
     return mRootObject;
 }
 
-sp<RpcConnection> RpcServer::addClientConnection() {
+void RpcServer::join() {
     LOG_ALWAYS_FATAL_IF(!mAgreedExperimental, "no!");
 
-    auto connection = RpcConnection::make();
-    connection->setForServer(sp<RpcServer>::fromExisting(this));
-    {
-        std::lock_guard<std::mutex> _l(mLock);
-        LOG_ALWAYS_FATAL_IF(mStarted,
-                            "currently only supports adding client connections at creation time");
-        mConnections.push_back(connection);
-    }
-    return connection;
-}
-
-void RpcServer::join() {
     std::vector<std::thread> pool;
     {
         std::lock_guard<std::mutex> _l(mLock);
+        LOG_ALWAYS_FATAL_IF(mServer.get() == -1, "RpcServer must be setup to join.");
+        // TODO(b/185167543): support more than one client at once
+        mConnection = RpcConnection::make();
+        mConnection->setForServer(sp<RpcServer>::fromExisting(this), 42 /*placeholder id*/);
+
         mStarted = true;
-        for (const sp<RpcConnection>& connection : mConnections) {
             for (size_t i = 0; i < mMaxThreads; i++) {
-                pool.push_back(std::thread([=] { connection->join(); }));
+                pool.push_back(std::thread([=] {
+                    // TODO(b/185167543): do this dynamically, instead of from a static number
+                    // of threads
+                    unique_fd clientFd(TEMP_FAILURE_RETRY(
+                            accept4(mServer.get(), nullptr, 0 /*length*/, SOCK_CLOEXEC)));
+                    if (clientFd < 0) {
+                        // If this log becomes confusing, should save more state from
+                        // setupUnixDomainServer in order to output here.
+                        ALOGE("Could not accept4 socket: %s", strerror(errno));
+                        return;
+                    }
+
+                    LOG_RPC_DETAIL("accept4 on fd %d yields fd %d", mServer.get(), clientFd.get());
+
+                    mConnection->join(std::move(clientFd));
+                }));
             }
-        }
     }
 
     // TODO(b/185167543): don't waste extra thread for join, and combine threads
@@ -98,4 +156,39 @@
     for (auto& t : pool) t.join();
 }
 
+std::vector<sp<RpcConnection>> RpcServer::listConnections() {
+    std::lock_guard<std::mutex> _l(mLock);
+    if (mConnection == nullptr) return {};
+    return {mConnection};
+}
+
+bool RpcServer::setupSocketServer(const RpcSocketAddress& addr) {
+    {
+        std::lock_guard<std::mutex> _l(mLock);
+        LOG_ALWAYS_FATAL_IF(mServer.get() != -1, "Each RpcServer can only have one server.");
+    }
+
+    unique_fd serverFd(
+            TEMP_FAILURE_RETRY(socket(addr.addr()->sa_family, SOCK_STREAM | SOCK_CLOEXEC, 0)));
+    if (serverFd == -1) {
+        ALOGE("Could not create socket: %s", strerror(errno));
+        return false;
+    }
+
+    if (0 != TEMP_FAILURE_RETRY(bind(serverFd.get(), addr.addr(), addr.addrSize()))) {
+        int savedErrno = errno;
+        ALOGE("Could not bind socket at %s: %s", addr.toString().c_str(), strerror(savedErrno));
+        return false;
+    }
+
+    if (0 != TEMP_FAILURE_RETRY(listen(serverFd.get(), 1 /*backlog*/))) {
+        int savedErrno = errno;
+        ALOGE("Could not listen socket at %s: %s", addr.toString().c_str(), strerror(savedErrno));
+        return false;
+    }
+
+    mServer = std::move(serverFd);
+    return true;
+}
+
 } // namespace android
diff --git a/libs/binder/RpcSocketAddress.h b/libs/binder/RpcSocketAddress.h
new file mode 100644
index 0000000..c6a06cf
--- /dev/null
+++ b/libs/binder/RpcSocketAddress.h
@@ -0,0 +1,122 @@
+/*
+ * Copyright (C) 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#pragma once
+
+#include <string>
+
+#include <arpa/inet.h>
+#include <netdb.h>
+#include <netinet/in.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <sys/un.h>
+
+#ifdef __BIONIC__
+#include <linux/vm_sockets.h>
+#endif
+
+namespace android {
+
+class RpcSocketAddress {
+public:
+    virtual ~RpcSocketAddress() {}
+    virtual std::string toString() const = 0;
+    virtual const sockaddr* addr() const = 0;
+    virtual size_t addrSize() const = 0;
+};
+
+class UnixSocketAddress : public RpcSocketAddress {
+public:
+    explicit UnixSocketAddress(const char* path) : mAddr({.sun_family = AF_UNIX}) {
+        unsigned int pathLen = strlen(path) + 1;
+        LOG_ALWAYS_FATAL_IF(pathLen > sizeof(mAddr.sun_path), "Socket path is too long: %u %s",
+                            pathLen, path);
+        memcpy(mAddr.sun_path, path, pathLen);
+    }
+    virtual ~UnixSocketAddress() {}
+    std::string toString() const override {
+        return String8::format("path '%.*s'", static_cast<int>(sizeof(mAddr.sun_path)),
+                               mAddr.sun_path)
+                .c_str();
+    }
+    const sockaddr* addr() const override { return reinterpret_cast<const sockaddr*>(&mAddr); }
+    size_t addrSize() const override { return sizeof(mAddr); }
+
+private:
+    sockaddr_un mAddr;
+};
+
+#ifdef __BIONIC__
+
+class VsockSocketAddress : public RpcSocketAddress {
+public:
+    VsockSocketAddress(unsigned int cid, unsigned int port)
+          : mAddr({
+                    .svm_family = AF_VSOCK,
+                    .svm_port = port,
+                    .svm_cid = cid,
+            }) {}
+    virtual ~VsockSocketAddress() {}
+    std::string toString() const override {
+        return String8::format("cid %u port %u", mAddr.svm_cid, mAddr.svm_port).c_str();
+    }
+    const sockaddr* addr() const override { return reinterpret_cast<const sockaddr*>(&mAddr); }
+    size_t addrSize() const override { return sizeof(mAddr); }
+
+private:
+    sockaddr_vm mAddr;
+};
+
+#endif // __BIONIC__
+
+class InetSocketAddress : public RpcSocketAddress {
+public:
+    InetSocketAddress(const sockaddr* sockAddr, size_t size, const char* addr, unsigned int port)
+          : mSockAddr(sockAddr), mSize(size), mAddr(addr), mPort(port) {}
+    [[nodiscard]] std::string toString() const override {
+        return String8::format("%s:%u", mAddr, mPort).c_str();
+    }
+    [[nodiscard]] const sockaddr* addr() const override { return mSockAddr; }
+    [[nodiscard]] size_t addrSize() const override { return mSize; }
+
+    using AddrInfo = std::unique_ptr<addrinfo, decltype(&freeaddrinfo)>;
+    static AddrInfo getAddrInfo(const char* addr, unsigned int port) {
+        addrinfo hint{
+                .ai_flags = 0,
+                .ai_family = AF_UNSPEC,
+                .ai_socktype = SOCK_STREAM,
+                .ai_protocol = 0,
+        };
+        addrinfo* aiStart = nullptr;
+        if (int rc = getaddrinfo(addr, std::to_string(port).data(), &hint, &aiStart); 0 != rc) {
+            ALOGE("Unable to resolve %s:%u: %s", addr, port, gai_strerror(rc));
+            return AddrInfo(nullptr, nullptr);
+        }
+        if (aiStart == nullptr) {
+            ALOGE("Unable to resolve %s:%u: getaddrinfo returns null", addr, port);
+            return AddrInfo(nullptr, nullptr);
+        }
+        return AddrInfo(aiStart, &freeaddrinfo);
+    }
+
+private:
+    const sockaddr* mSockAddr;
+    size_t mSize;
+    const char* mAddr;
+    unsigned int mPort;
+};
+
+} // namespace android
diff --git a/libs/binder/RpcState.cpp b/libs/binder/RpcState.cpp
index 6bfcc42..19dea7e 100644
--- a/libs/binder/RpcState.cpp
+++ b/libs/binder/RpcState.cpp
@@ -249,7 +249,7 @@
 }
 
 status_t RpcState::getMaxThreads(const base::unique_fd& fd, const sp<RpcConnection>& connection,
-                                 size_t* maxThreads) {
+                                 size_t* maxThreadsOut) {
     Parcel data;
     data.markForRpc(connection);
     Parcel reply;
@@ -261,15 +261,36 @@
         return status;
     }
 
-    int32_t threads;
-    status = reply.readInt32(&threads);
+    int32_t maxThreads;
+    status = reply.readInt32(&maxThreads);
     if (status != OK) return status;
-    if (threads <= 0) {
-        ALOGE("Error invalid max threads: %d", threads);
+    if (maxThreads <= 0) {
+        ALOGE("Error invalid max maxThreads: %d", maxThreads);
         return BAD_VALUE;
     }
 
-    *maxThreads = threads;
+    *maxThreadsOut = maxThreads;
+    return OK;
+}
+
+status_t RpcState::getConnectionId(const base::unique_fd& fd, const sp<RpcConnection>& connection,
+                                   int32_t* connectionIdOut) {
+    Parcel data;
+    data.markForRpc(connection);
+    Parcel reply;
+
+    status_t status = transact(fd, RpcAddress::zero(), RPC_SPECIAL_TRANSACT_GET_CONNECTION_ID, data,
+                               connection, &reply, 0);
+    if (status != OK) {
+        ALOGE("Error getting connection ID: %s", statusToString(status).c_str());
+        return status;
+    }
+
+    int32_t connectionId;
+    status = reply.readInt32(&connectionId);
+    if (status != OK) return status;
+
+    *connectionIdOut = connectionId;
     return OK;
 }
 
@@ -554,6 +575,16 @@
                         replyStatus = reply.writeInt32(server->getMaxThreads());
                         break;
                     }
+                    case RPC_SPECIAL_TRANSACT_GET_CONNECTION_ID: {
+                        // only connections w/ services can be the source of a
+                        // connection ID (so still guarded by non-null server)
+                        //
+                        // connections associated with servers must have an ID
+                        // (hence abort)
+                        int32_t id = connection->getPrivateAccessorForId().get().value();
+                        replyStatus = reply.writeInt32(id);
+                        break;
+                    }
                     default: {
                         replyStatus = UNKNOWN_TRANSACTION;
                     }
diff --git a/libs/binder/RpcState.h b/libs/binder/RpcState.h
index 1cfa406..825fd7c 100644
--- a/libs/binder/RpcState.h
+++ b/libs/binder/RpcState.h
@@ -50,9 +50,12 @@
     RpcState();
     ~RpcState();
 
+    // TODO(b/182940634): combine some special transactions into one "getServerInfo" call?
     sp<IBinder> getRootObject(const base::unique_fd& fd, const sp<RpcConnection>& connection);
     status_t getMaxThreads(const base::unique_fd& fd, const sp<RpcConnection>& connection,
                            size_t* maxThreadsOut);
+    status_t getConnectionId(const base::unique_fd& fd, const sp<RpcConnection>& connection,
+                             int32_t* connectionIdOut);
 
     [[nodiscard]] status_t transact(const base::unique_fd& fd, const RpcAddress& address,
                                     uint32_t code, const Parcel& data,
diff --git a/libs/binder/RpcWireFormat.h b/libs/binder/RpcWireFormat.h
index cc7cacb..56af0d3 100644
--- a/libs/binder/RpcWireFormat.h
+++ b/libs/binder/RpcWireFormat.h
@@ -48,6 +48,7 @@
 enum : uint32_t {
     RPC_SPECIAL_TRANSACT_GET_ROOT = 0,
     RPC_SPECIAL_TRANSACT_GET_MAX_THREADS = 1,
+    RPC_SPECIAL_TRANSACT_GET_CONNECTION_ID = 2,
 };
 
 // serialization is like:
diff --git a/libs/binder/include/binder/RpcConnection.h b/libs/binder/include/binder/RpcConnection.h
index 3a2d8e5..7e31e8a 100644
--- a/libs/binder/include/binder/RpcConnection.h
+++ b/libs/binder/include/binder/RpcConnection.h
@@ -32,6 +32,7 @@
 
 class Parcel;
 class RpcServer;
+class RpcSocketAddress;
 class RpcState;
 
 /**
@@ -43,19 +44,6 @@
     static sp<RpcConnection> make();
 
     /**
-     * This represents a connection for responses, e.g.:
-     *
-     *     process A serves binder a
-     *     process B opens a connection to process A
-     *     process B makes binder b and sends it to A
-     *     A uses this 'back connection' to send things back to B
-     *
-     * This should be called once, and then a call should be made to join per
-     * connection thread.
-     */
-    [[nodiscard]] bool setupUnixDomainServer(const char* path);
-
-    /**
      * This should be called once per thread, matching 'join' in the remote
      * process.
      */
@@ -63,28 +51,12 @@
 
 #ifdef __BIONIC__
     /**
-     * Creates an RPC server at the current port.
-     */
-    [[nodiscard]] bool setupVsockServer(unsigned int port);
-
-    /**
      * Connects to an RPC server at the CVD & port.
      */
     [[nodiscard]] bool setupVsockClient(unsigned int cvd, unsigned int port);
 #endif // __BIONIC__
 
     /**
-     * Creates an RPC server at the current port using IPv4.
-     *
-     * TODO(b/182914638): IPv6 support
-     *
-     * Set |port| to 0 to pick an ephemeral port; see discussion of
-     * /proc/sys/net/ipv4/ip_local_port_range in ip(7). In this case, |assignedPort|
-     * will be set to the picked port number, if it is not null.
-     */
-    [[nodiscard]] bool setupInetServer(unsigned int port, unsigned int* assignedPort);
-
-    /**
      * Connects to an RPC server at the given address and port.
      */
     [[nodiscard]] bool setupInetClient(const char* addr, unsigned int port);
@@ -116,26 +88,32 @@
 
     ~RpcConnection();
 
-    void setForServer(const wp<RpcServer>& server);
     wp<RpcServer> server();
 
     // internal only
     const std::unique_ptr<RpcState>& state() { return mState; }
 
-    class SocketAddress {
-    public:
-        virtual ~SocketAddress();
-        virtual std::string toString() const = 0;
-        virtual const sockaddr* addr() const = 0;
-        virtual size_t addrSize() const = 0;
+    class PrivateAccessorForId {
+    private:
+        friend class RpcConnection;
+        friend class RpcState;
+        explicit PrivateAccessorForId(const RpcConnection* connection) : mConnection(connection) {}
+
+        const std::optional<int32_t> get() { return mConnection->mId; }
+
+        const RpcConnection* mConnection;
     };
+    PrivateAccessorForId getPrivateAccessorForId() const { return PrivateAccessorForId(this); }
 
 private:
+    friend PrivateAccessorForId;
     friend sp<RpcConnection>;
     friend RpcServer;
     RpcConnection();
 
-    void join();
+    status_t readId();
+
+    void join(base::unique_fd client);
 
     struct ConnectionSocket : public RefBase {
         base::unique_fd fd;
@@ -145,11 +123,11 @@
         std::optional<pid_t> exclusiveTid;
     };
 
-    bool setupSocketServer(const SocketAddress& address);
-    bool setupSocketClient(const SocketAddress& address);
-    bool setupOneSocketClient(const SocketAddress& address);
-    void addClient(base::unique_fd&& fd);
-    sp<ConnectionSocket> assignServerToThisThread(base::unique_fd&& fd);
+    bool setupSocketClient(const RpcSocketAddress& address);
+    bool setupOneSocketClient(const RpcSocketAddress& address);
+    void addClient(base::unique_fd fd);
+    void setForServer(const wp<RpcServer>& server, int32_t connectionId);
+    sp<ConnectionSocket> assignServerToThisThread(base::unique_fd fd);
     bool removeServerSocket(const sp<ConnectionSocket>& socket);
 
     enum class SocketUse {
@@ -195,9 +173,10 @@
 
     wp<RpcServer> mForServer; // maybe null, for client connections
 
-    std::unique_ptr<RpcState> mState;
+    // TODO(b/183988761): this shouldn't be guessable
+    std::optional<int32_t> mId;
 
-    base::unique_fd mServer; // socket we are accepting connections on
+    std::unique_ptr<RpcState> mState;
 
     std::mutex mSocketMutex;           // for all below
     std::condition_variable mSocketCv; // for mWaitingThreads
diff --git a/libs/binder/include/binder/RpcServer.h b/libs/binder/include/binder/RpcServer.h
index 9247128..5535d8a 100644
--- a/libs/binder/include/binder/RpcServer.h
+++ b/libs/binder/include/binder/RpcServer.h
@@ -29,14 +29,52 @@
 
 namespace android {
 
+class RpcSocketAddress;
+
 /**
  * This represents a server of an interface, which may be connected to by any
  * number of clients over sockets.
+ *
+ * Usage:
+ *     auto server = RpcServer::make();
+ *     // only supports one now
+ *     if (!server->setup*Server(...)) {
+ *         :(
+ *     }
+ *     server->join();
  */
 class RpcServer final : public virtual RefBase {
 public:
     static sp<RpcServer> make();
 
+    /**
+     * This represents a connection for responses, e.g.:
+     *
+     *     process A serves binder a
+     *     process B opens a connection to process A
+     *     process B makes binder b and sends it to A
+     *     A uses this 'back connection' to send things back to B
+     */
+    [[nodiscard]] bool setupUnixDomainServer(const char* path);
+
+#ifdef __BIONIC__
+    /**
+     * Creates an RPC server at the current port.
+     */
+    [[nodiscard]] bool setupVsockServer(unsigned int port);
+#endif // __BIONIC__
+
+    /**
+     * Creates an RPC server at the current port using IPv4.
+     *
+     * TODO(b/182914638): IPv6 support
+     *
+     * Set |port| to 0 to pick an ephemeral port; see discussion of
+     * /proc/sys/net/ipv4/ip_local_port_range in ip(7). In this case, |assignedPort|
+     * will be set to the picked port number, if it is not null.
+     */
+    [[nodiscard]] bool setupInetServer(unsigned int port, unsigned int* assignedPort);
+
     void iUnderstandThisCodeIsExperimentalAndIWillNotUseItInProduction();
 
     /**
@@ -58,33 +96,31 @@
     sp<IBinder> getRootObject();
 
     /**
-     * Setup a static connection, when the number of clients are known.
-     *
-     * Each call to this function corresponds to a different client, and clients
-     * each have their own threadpools.
-     *
-     * TODO(b/167966510): support dynamic creation of connections/threads
-     */
-    sp<RpcConnection> addClientConnection();
-
-    /**
      * You must have at least one client connection before calling this.
      */
     void join();
 
+    /**
+     * For debugging!
+     */
+    std::vector<sp<RpcConnection>> listConnections();
+
     ~RpcServer();
 
 private:
     friend sp<RpcServer>;
     RpcServer();
 
+    bool setupSocketServer(const RpcSocketAddress& address);
+
     bool mAgreedExperimental = false;
     bool mStarted = false; // TODO(b/185167543): support dynamically added clients
     size_t mMaxThreads = 1;
+    base::unique_fd mServer; // socket we are accepting connections on
 
     std::mutex mLock; // for below
     sp<IBinder> mRootObject;
-    std::vector<sp<RpcConnection>> mConnections; // per-client
+    sp<RpcConnection> mConnection;
 };
 
 } // namespace android
diff --git a/libs/binder/tests/binderRpcBenchmark.cpp b/libs/binder/tests/binderRpcBenchmark.cpp
index b3282ff..ce47c0d 100644
--- a/libs/binder/tests/binderRpcBenchmark.cpp
+++ b/libs/binder/tests/binderRpcBenchmark.cpp
@@ -121,12 +121,8 @@
     std::thread([addr]() {
         sp<RpcServer> server = RpcServer::make();
         server->setRootObject(sp<MyBinderRpcBenchmark>::make());
-
         server->iUnderstandThisCodeIsExperimentalAndIWillNotUseItInProduction();
-
-        sp<RpcConnection> connection = server->addClientConnection();
-        CHECK(connection->setupUnixDomainServer(addr.c_str()));
-
+        CHECK(server->setupUnixDomainServer(addr.c_str()));
         server->join();
     }).detach();
 
diff --git a/libs/binder/tests/binderRpcTest.cpp b/libs/binder/tests/binderRpcTest.cpp
index f3ec904..d23df8e 100644
--- a/libs/binder/tests/binderRpcTest.cpp
+++ b/libs/binder/tests/binderRpcTest.cpp
@@ -78,7 +78,7 @@
 
 class MyBinderRpcTest : public BnBinderRpcTest {
 public:
-    sp<RpcConnection> connection;
+    wp<RpcServer> server;
 
     Status sendString(const std::string& str) override {
         (void)str;
@@ -89,13 +89,23 @@
         return Status::ok();
     }
     Status countBinders(int32_t* out) override {
-        if (connection == nullptr) {
+        sp<RpcServer> spServer = server.promote();
+        if (spServer == nullptr) {
             return Status::fromExceptionCode(Status::EX_NULL_POINTER);
         }
-        *out = connection->state()->countBinders();
-        if (*out != 1) {
-            connection->state()->dump();
+        size_t count = 0;
+        for (auto connection : spServer->listConnections()) {
+            count += connection->state()->countBinders();
         }
+        // help debugging if we don't have one binder (this call is always made
+        // in this test when exactly one binder is held, which is held only to
+        // call this method - all other binders should be cleaned up)
+        if (count != 1) {
+            for (auto connection : spServer->listConnections()) {
+                connection->state()->dump();
+            }
+        }
+        *out = count;
         return Status::ok();
     }
     Status pingMe(const sp<IBinder>& binder, int32_t* out) override {
@@ -296,8 +306,7 @@
     // This creates a new process serving an interface on a certain number of
     // threads.
     ProcessConnection createRpcTestSocketServerProcess(
-            size_t numThreads,
-            const std::function<void(const sp<RpcServer>&, const sp<RpcConnection>&)>& configure) {
+            size_t numThreads, const std::function<void(const sp<RpcServer>&)>& configure) {
         SocketType socketType = GetParam();
 
         std::string addr = allocateSocketAddress();
@@ -312,21 +321,18 @@
                     server->iUnderstandThisCodeIsExperimentalAndIWillNotUseItInProduction();
                     server->setMaxThreads(numThreads);
 
-                    // server supporting one client on one socket
-                    sp<RpcConnection> connection = server->addClientConnection();
-
                     switch (socketType) {
                         case SocketType::UNIX:
-                            CHECK(connection->setupUnixDomainServer(addr.c_str())) << addr;
+                            CHECK(server->setupUnixDomainServer(addr.c_str())) << addr;
                             break;
 #ifdef __BIONIC__
                         case SocketType::VSOCK:
-                            CHECK(connection->setupVsockServer(vsockPort));
+                            CHECK(server->setupVsockServer(vsockPort));
                             break;
 #endif // __BIONIC__
                         case SocketType::INET: {
                             unsigned int outPort = 0;
-                            CHECK(connection->setupInetServer(0, &outPort));
+                            CHECK(server->setupInetServer(0, &outPort));
                             CHECK_NE(0, outPort);
                             CHECK(android::base::WriteFully(pipe->writeEnd(), &outPort,
                                                             sizeof(outPort)));
@@ -336,7 +342,7 @@
                             LOG_ALWAYS_FATAL("Unknown socket type");
                     }
 
-                    configure(server, connection);
+                    configure(server);
 
                     server->join();
                 }),
@@ -379,13 +385,11 @@
     BinderRpcTestProcessConnection createRpcTestSocketServerProcess(size_t numThreads) {
         BinderRpcTestProcessConnection ret{
                 .proc = createRpcTestSocketServerProcess(numThreads,
-                                                         [&](const sp<RpcServer>& server,
-                                                             const sp<RpcConnection>& connection) {
+                                                         [&](const sp<RpcServer>& server) {
                                                              sp<MyBinderRpcTest> service =
                                                                      new MyBinderRpcTest;
                                                              server->setRootObject(service);
-                                                             service->connection =
-                                                                     connection; // for testing only
+                                                             service->server = server;
                                                          }),
         };
 
@@ -397,12 +401,10 @@
 };
 
 TEST_P(BinderRpc, RootObjectIsNull) {
-    auto proc = createRpcTestSocketServerProcess(1,
-                                                 [](const sp<RpcServer>& server,
-                                                    const sp<RpcConnection>&) {
-                                                     // this is the default, but to be explicit
-                                                     server->setRootObject(nullptr);
-                                                 });
+    auto proc = createRpcTestSocketServerProcess(1, [](const sp<RpcServer>& server) {
+        // this is the default, but to be explicit
+        server->setRootObject(nullptr);
+    });
 
     // retrieved by getRootObject when process is created above
     EXPECT_EQ(nullptr, proc.rootBinder);