How to Connect to Binance FIX API? Authentication and Connection Verification

Binance FIX API connection issues usually do not stem from the protocol itself, but from the authentication step. The most common failure mode is: TCP connection succeeds, TLS handshake completes, but after sending the Logon message the server gives no response and disconnects after a few seconds. This "silent disconnect" almost always means a field in the Logon message does not meet requirements, rather than a network problem.

Binance Exchange
The world's largest cryptocurrency exchange by trading volume,leading in security and liquidity.
New user benefit: Enjoy 20% off trading fees upon registration!

Register Now App Download

First Confirm Account and Key Eligibility

FIX API is not available to all Binance users. It only supports Binance Spot, not futures or margin trading. Before accessing a FIX session, you need to create an Ed25519 API key on the Binance API management page and grant it the corresponding permission: "Enable FIX API Trading" for order sessions or "Enable FIX API Reading" for read-only sessions.

HMAC SHA-256 and RSA keys cannot be used for FIX sessions. If you use these key types, the connection will be rejected directly.

Logon Message Construction Rules

The first message of a FIX session must be Logon (MsgType = A) and must meet several hard requirements. Otherwise the server will not return any error description and will simply disconnect silently.

The protocol version must be FIX.4.4. This is the most common cause of silent disconnection. If you write 8=FIX.4.2 in the message header, the server will not prompt a version error; it will simply not respond and then disconnect.

The format of SenderCompID (49) and TargetCompID (56) must match Binance requirements. For spot order sessions, TargetCompID is usually SPOT. SenderCompID is the value you set yourself in the API key management page.

RawData (96) signature is the core of authentication. It is a Base64-encoded Ed25519 signature. The signed content is formed by concatenating five fields in order, separated by SOH (ASCII 1):

1. MsgType (i.e., A)
2. SenderCompID (your field 49 value)
3. TargetCompID (your field 56 value)
4. MsgSeqNum (message sequence number)
5. SendingTime

You need to sign this concatenated string with the Ed25519 private key generated when you created the API key, then Base64-encode it and fill it into the RawData field.

Fill the Username (553) field with your API key itself, not the private key.

Two Key TLS Configuration Points

FIX API requires a TCP + TLS connection. A plaintext TCP connection will receive no response because the server is waiting for the TLS handshake.

If your client library does not natively support TLS, for example some FIX libraries only handle application-layer messages, you can use a local proxy such as stunnel to wrap TLS. When configuring stunnel, pay attention to two easily overlooked parameters:

SNI (Server Name Indication) must be sent. Binance updated its FIX TLS configuration in June 2026, requiring clients to send SNI during the TLS handshake and verify the certificate against the requested hostname. Clients that do not send SNI will get a certificate error during the handshake, causing the connection to fail. Some Node.js clients trigger this problem if SNI is not explicitly configured.

Certificate verification cannot be skipped. In stunnel configuration, set verifyChain = yes and checkHost = fix-oe.binance.com or the corresponding testnet/demo domain to ensure you are connecting to Binance's legitimate server, not a man-in-the-middle.

Connection Verification: Testnet First, Then Production

Binance provides Testnet and Demo Mode environments for verifying FIX connections without using real funds.

The Testnet FIX order session endpoint is fix-oe.testnet.binance.vision:9000. You need to create a separate Ed25519 API key at testnet.binance.vision first, then use that key to construct the Logon message. If Logon succeeds, you will receive a Logon response with MsgType = A, containing the server's HeartBtInt and SessionStatus information.

Demo Mode uses the same endpoint format as production but with a different domain: demo-fix-oe.binance.com:9000. Demo Mode uses the real API endpoint but only performs simulated matching. It is suitable for final connection stability testing after Testnet verification and before going live.

Verification success criteria: after sending Logon, you receive a Logon response from the server within a reasonable time, usually within 1 second. The response has MsgType = A and no Reject message with MsgType = 3. If you receive a Logon rejection saying "Signature for this request is not valid", it means the signature content or encoding is wrong. Check the concatenation order, SOH separator, and Base64 encoding.

Troubleshooting Common Silent Disconnects

If the connection succeeds but there is no response after Logon before disconnection, check in this order:

1. Does the message header start with 8=FIX.4.4? This is the most frequent cause.
2. Is TLS actually enabled? Use a packet capture tool or stunnel log to confirm the handshake actually completed, rather than sending messages on a plaintext port.
3. Does the RawData signature concatenation match the documentation? The order of the five fields, SOH separator, and ASCII encoding must all be correct.
4. Does the API key have FIX permission? Confirm on the API management page that the corresponding FIX permission is checked.
5. Does SenderCompID match the key configuration? Binance requires you to specify a SenderCompID for the FIX session, and this value needs to be associated with the API key.

If all of the above are confirmed but the problem persists, you can post on the Binance developer community with the complete Logon message, using | instead of SOH for readability, and the stunnel log. You can usually get a more specific diagnosis.

Binance Exchange
The world's largest cryptocurrency exchange by trading volume,leading in security and liquidity.
New user benefit: Enjoy 20% off trading fees upon registration!

Register Now App Download

References

1. Binance Developer Community·Disconnected from FIX without feedback upon sending a LOGON message，页面发布或更新日期：2025-11-10；核查日期：2026-10-02。
2. Binance Open Platform·FIX API，页面发布或更新日期：2026-09-24；核查日期：2026-10-02。
3. Binance Support·币安现货API服务升级公告，页面发布或更新日期：2024-08-05；核查日期：2026-10-02。
4. DeepWiki·FIX Connection and Authentication | binance/binance-spot-api-docs，页面发布或更新日期：2026-04-13；核查日期：2026-10-02。
5. Binance Open Platform·FIX API，页面未标明更新日期；核查日期：2026-10-02。
6. DeepWiki·FIX API | binance/binance-spot-api-docs，页面发布或更新日期：2026-04-13；核查日期：2026-10-02。
7. Binance Developer Community·Problems getting responses on Fix API test server，页面发布或更新日期：2024-10-09；核查日期：2026-10-02。
8. Binance ME·Notice on Binance Spot API Update (2026-03-12)，页面发布或更新日期：2026-03-11；核查日期：2026-10-02。
9. Binance·现货模拟交易，页面发布或更新日期：2026-09-10；核查日期：2026-10-02。
10. Binance·Demo Mode for SPOT Trading，页面发布或更新日期：2026-09-14；核查日期：2026-10-02。
11. Stack Overflow·Fix Protocol quickfix c++: RawData (tag 96) requires base64 encoded signature，页面发布或更新日期：2025-01-01；核查日期：2026-10-02。