Connection

This page covers the functions that drive the connection lifecycle of a FreeRDP client: establishing the session, pumping the event loop, disconnecting, and interpreting errors.

Overview

freerdp_connect()
      │
      ▼
  PreConnect callback
      │
      ▼
  [TCP / TLS / NLA negotiation]
      │
      ▼
  PostConnect callback
      │
      ▼
  ┌─────────────────────────────┐
  │  event loop                 │
  │  freerdp_get_event_handles()│
  │  WaitForMultipleObjects()   │
  │  freerdp_check_event_       │
  │     handles()              │
  └─────────────────────────────┘
      │
      ▼
  PostDisconnect callback
      │
      ▼
  freerdp_disconnect()

Connecting

BOOL freerdp_connect(freerdp* instance);

Performs the full RDP connection sequence:

Calls instance->PreConnect (if set).
Establishes the TCP connection, negotiates security (TLS/NLA), and completes the RDP handshake.
Calls instance->PostConnect on success.

Returns TRUE on success, FALSE on failure. On failure, call freerdp_get_last_error() for a detailed error code.

freerdp_connect() blocks until the connection sequence completes or fails. Run it in a dedicated thread (as shown in the sample client) to keep your UI responsive.

Disconnecting

/* Graceful disconnect */
BOOL freerdp_disconnect(freerdp* instance);

/* Signal an abort from any thread (non-blocking) */
BOOL freerdp_abort_connect_context(rdpContext* context);

/* Query whether a disconnect has been requested */
BOOL freerdp_shall_disconnect_context(const rdpContext* context);

/* Get a waitable HANDLE that becomes signaled when abort is requested */
HANDLE freerdp_abort_event(rdpContext* context);

freerdp_abort_connect_context() is safe to call from any thread. It signals the connection to shut down; the event loop should detect this and exit, after which freerdp_disconnect() cleans up.

Reconnecting

BOOL freerdp_reconnect(freerdp* instance);
BOOL freerdp_disconnect_before_reconnect_context(rdpContext* context);

To reconnect after a dropped session:

Call freerdp_disconnect_before_reconnect_context() to cleanly prepare the instance for reconnection without fully tearing down all state.
Call freerdp_reconnect() which re-runs the connection sequence.

The client-common helper client_auto_reconnect_ex() wraps this pattern with automatic retry logic:

BOOL client_auto_reconnect(freerdp* instance);
BOOL client_auto_reconnect_ex(freerdp* instance,
                               BOOL (*window_events)(freerdp* instance));

Event Loop

FreeRDP is event-driven. After a successful freerdp_connect(), your thread must call these two functions in a loop:

/* Retrieve OS event handles (sockets, timers, etc.) */
DWORD freerdp_get_event_handles(rdpContext* context,
                                 HANDLE* events,
                                 DWORD count);

/* Process all pending events on those handles */
BOOL freerdp_check_event_handles(rdpContext* context);

freerdp_get_event_handles() returns the number of handles written, or 0 on error. freerdp_check_event_handles() returns FALSE if an unrecoverable error occurred; check freerdp_get_last_error() to distinguish a protocol-level disconnect from a real error.

Canonical Event Loop

static DWORD run_session(freerdp* instance)
{
    DWORD result = 0;
    HANDLE handles[MAXIMUM_WAIT_OBJECTS];

    BOOL connected = freerdp_connect(instance);
    if (!connected)
    {
        result = freerdp_get_last_error(instance->context);
        return result;
    }

    while (!freerdp_shall_disconnect_context(instance->context))
    {
        DWORD nCount = freerdp_get_event_handles(instance->context,
                                                  handles,
                                                  ARRAYSIZE(handles));
        if (nCount == 0)
            break;  /* error */

        DWORD status = WaitForMultipleObjects(nCount, handles, FALSE, INFINITE);
        if (status == WAIT_FAILED)
            break;

        if (!freerdp_check_event_handles(instance->context))
        {
            /* Only treat as an error when no disconnect code is set */
            if (freerdp_get_last_error(instance->context) == FREERDP_ERROR_SUCCESS)
                result = 1;  /* unexpected failure */
            break;
        }
    }

    freerdp_disconnect(instance);
    return result;
}

Error Handling

Context-level error

/* Read the last error code */
UINT32 freerdp_get_last_error(const rdpContext* context);

/* Human-readable string for an error code */
const char* freerdp_get_last_error_string(UINT32 code);

/* Short name (e.g. "FREERDP_ERROR_DNS_NAME_NOT_FOUND") */
const char* freerdp_get_last_error_name(UINT32 code);

/* Category string (e.g. "use", "protocol", "server") */
const char* freerdp_get_last_error_category(UINT32 code);

Error codes are composed from a class and a type:

#define MAKE_FREERDP_ERROR(_class, _type) \
    (((FREERDP_ERROR_##_class##_CLASS) << 16) | (_type))

Connection Error Codes (`FREERDP_ERROR_CONNECT_*`)

These are the most common codes returned by freerdp_get_last_error() after a failed freerdp_connect():

Constant	Meaning
`FREERDP_ERROR_SUCCESS`	No error
`FREERDP_ERROR_PRE_CONNECT_FAILED`	`PreConnect` callback returned `FALSE`
`FREERDP_ERROR_POST_CONNECT_FAILED`	`PostConnect` callback returned `FALSE`
`FREERDP_ERROR_DNS_ERROR`	DNS resolution failed
`FREERDP_ERROR_DNS_NAME_NOT_FOUND`	Hostname could not be resolved
`FREERDP_ERROR_CONNECT_FAILED`	TCP connection refused or timed out
`FREERDP_ERROR_TLS_CONNECT_FAILED`	TLS handshake failed
`FREERDP_ERROR_AUTHENTICATION_FAILED`	Credentials rejected
`FREERDP_ERROR_SECURITY_NEGO_CONNECT_FAILED`	Protocol negotiation failed
`FREERDP_ERROR_CONNECT_CANCELLED`	Connection was aborted by the client
`FREERDP_ERROR_CONNECT_LOGON_FAILURE`	Logon failure (wrong credentials)
`FREERDP_ERROR_CONNECT_WRONG_PASSWORD`	Incorrect password
`FREERDP_ERROR_CONNECT_ACCOUNT_LOCKED_OUT`	Account locked out
`FREERDP_ERROR_CONNECT_ACCOUNT_EXPIRED`	Account expired
`FREERDP_ERROR_CONNECT_PASSWORD_EXPIRED`	Password expired
`FREERDP_ERROR_CONNECT_PASSWORD_MUST_CHANGE`	Password must be changed before login
`FREERDP_ERROR_CONNECT_ACCESS_DENIED`	Access denied
`FREERDP_ERROR_CONNECT_NO_OR_MISSING_CREDENTIALS`	No credentials available
`FREERDP_ERROR_CONNECT_KDC_UNREACHABLE`	Kerberos KDC not reachable

Server-sent Error Info (`freerdp_error_info()`)

The server can push an Error Info PDU to explain why it is disconnecting:

/* Returns the ERRINFO_* code from the last Error Info PDU, or 0 */
UINT32 freerdp_error_info(const freerdp* instance);

/* Human-readable string for an ERRINFO code */
const char* freerdp_get_error_info_string(UINT32 code);
const char* freerdp_get_error_info_name(UINT32 code);

Common ERRINFO_* codes:

Constant	Meaning
`ERRINFO_RPC_INITIATED_DISCONNECT`	Server-initiated disconnect
`ERRINFO_IDLE_TIMEOUT`	Session idle timeout
`ERRINFO_LOGON_TIMEOUT`	Logon timeout
`ERRINFO_DISCONNECTED_BY_OTHER_CONNECTION`	Another connection displaced this session
`ERRINFO_OUT_OF_MEMORY`	Server out of memory
`ERRINFO_SERVER_DENIED_CONNECTION`	Server refused the connection
`ERRINFO_LICENSE_NO_LICENSE_SERVER`	No license server reachable
`ERRINFO_LICENSE_NO_LICENSE`	No valid license available

Connection State

/* Query the current connection state */
CONNECTION_STATE freerdp_get_state(const rdpContext* context);

/* Stringify a CONNECTION_STATE value */
const char* freerdp_state_string(CONNECTION_STATE state);

/* TRUE if the connection is fully established and active */
BOOL freerdp_is_active_state(const rdpContext* context);

Disconnect Reason

After a disconnect you can retrieve the MCS-level ultimatum reason:

int freerdp_get_disconnect_ultimatum(const rdpContext* context);
const char* freerdp_disconnect_reason_string(int reason);

Possible values are defined by enum Disconnect_Ultimatum: domain_disconnected, provider_initiated, token_purged, user_requested, channel_purged.

Complete Example

This example mirrors the structure of the FreeRDP sample client (client/Sample/tf_freerdp.c):

#include <freerdp/freerdp.h>
#include <freerdp/client.h>
#include <freerdp/gdi/gdi.h>
#include <freerdp/log.h>
#include <winpr/synch.h>

/* --- Callbacks --- */

static BOOL my_pre_connect(freerdp* instance)
{
    rdpSettings* s = instance->context->settings;
    freerdp_settings_set_bool(s, FreeRDP_CertificateCallbackPreferPEM, TRUE);
    /* Subscribe to channel events here */
    return TRUE;
}

static BOOL my_post_connect(freerdp* instance)
{
    if (!gdi_init(instance, PIXEL_FORMAT_XRGB32))
        return FALSE;
    instance->context->update->BeginPaint = my_begin_paint;
    instance->context->update->EndPaint   = my_end_paint;
    return TRUE;
}

static void my_post_disconnect(freerdp* instance)
{
    gdi_free(instance);
}

static DWORD my_verify_cert(freerdp* instance, const char* host, UINT16 port,
                             const char* cn, const char* subject,
                             const char* issuer, const char* fp, DWORD flags)
{
    /* Present cert info to user, return 2 to accept for this session */
    (void)instance; (void)host; (void)port; (void)cn;
    (void)subject; (void)issuer; (void)fp; (void)flags;
    return 2;
}

/* --- Entry points --- */

static BOOL my_client_new(freerdp* instance, rdpContext* context)
{
    instance->PreConnect          = my_pre_connect;
    instance->PostConnect         = my_post_connect;
    instance->PostDisconnect      = my_post_disconnect;
    instance->VerifyCertificateEx = my_verify_cert;
    return TRUE;
}

static void my_client_free(freerdp* instance, rdpContext* context)
{
    (void)instance; (void)context;
}

static int my_client_start(rdpContext* ctx) { return 0; }
static int my_client_stop(rdpContext* ctx)  { return 0; }

/* --- Main thread proc --- */

static DWORD run_session(freerdp* instance)
{
    DWORD result  = 0;
    DWORD nCount  = 0;
    DWORD status  = 0;
    HANDLE handles[MAXIMUM_WAIT_OBJECTS];

    if (!freerdp_connect(instance))
    {
        result = freerdp_get_last_error(instance->context);
        WLog_ERR("myapp", "freerdp_connect failed: %s",
                 freerdp_get_last_error_string(result));
        return result;
    }

    while (!freerdp_shall_disconnect_context(instance->context))
    {
        nCount = freerdp_get_event_handles(instance->context,
                                            handles, ARRAYSIZE(handles));
        if (nCount == 0)
            break;

        status = WaitForMultipleObjects(nCount, handles, FALSE, INFINITE);
        if (status == WAIT_FAILED)
            break;

        if (!freerdp_check_event_handles(instance->context))
        {
            if (freerdp_get_last_error(instance->context) == FREERDP_ERROR_SUCCESS)
                WLog_ERR("myapp", "freerdp_check_event_handles failed");
            break;
        }
    }

    /* Check server disconnect reason */
    UINT32 ei = freerdp_error_info(instance);
    if (ei != 0 && ei != ERRINFO_NONE)
        WLog_INFO("myapp", "Server disconnect reason: %s",
                  freerdp_get_error_info_string(ei));

    freerdp_disconnect(instance);
    return result;
}

/* --- Entry point --- */

int main(int argc, char* argv[])
{
    int rc = 1;

    RDP_CLIENT_ENTRY_POINTS ep = { 0 };
    ep.Version     = RDP_CLIENT_INTERFACE_VERSION;
    ep.Size        = sizeof(RDP_CLIENT_ENTRY_POINTS_V1);
    ep.ContextSize = sizeof(rdpClientContext);
    ep.ClientNew   = my_client_new;
    ep.ClientFree  = my_client_free;
    ep.ClientStart = my_client_start;
    ep.ClientStop  = my_client_stop;

    rdpContext* ctx = freerdp_client_context_new(&ep);
    if (!ctx)
        return rc;

    /* Parse command line into settings */
    int status = freerdp_client_settings_parse_command_line(
                     ctx->settings, argc, argv, FALSE);
    if (status)
    {
        rc = freerdp_client_settings_command_line_status_print(
                 ctx->settings, status, argc, argv);
        goto done;
    }

    /* Set target explicitly if not provided via command line */
    freerdp_settings_set_string(ctx->settings, FreeRDP_ServerHostname, "rdp.example.com");
    freerdp_settings_set_uint32(ctx->settings, FreeRDP_ServerPort, 3389);

    if (freerdp_client_start(ctx) != 0)
        goto done;

    rc = (int)run_session(ctx->instance);

    freerdp_client_stop(ctx);
done:
    freerdp_client_context_free(ctx);
    return rc;
}

Client API

Server API

Channels

Utilities

Overview

Connecting

Disconnecting

Reconnecting

Event Loop

Canonical Event Loop

Error Handling

Context-level error

Connection Error Codes (`FREERDP_ERROR_CONNECT_*`)

Server-sent Error Info (`freerdp_error_info()`)

Connection State

Disconnect Reason

Complete Example

Client API

Server API

Channels

Utilities

​Overview

​Connecting

​Disconnecting

​Reconnecting

​Event Loop

​Canonical Event Loop

​Error Handling

​Context-level error

​Connection Error Codes (FREERDP_ERROR_CONNECT_*)

​Server-sent Error Info (freerdp_error_info())

​Connection State

​Disconnect Reason

​Complete Example

Overview

Connecting

Disconnecting

Reconnecting

Event Loop

Canonical Event Loop

Error Handling

Context-level error

Connection Error Codes (`FREERDP_ERROR_CONNECT_*`)

Server-sent Error Info (`freerdp_error_info()`)

Connection State

Disconnect Reason

Complete Example