Version: Next

Socket

Socket sink connector

Support Those Engines

Spark
Flink
SeaTunnel Zeta

Key features

exactly-once

Description

Used to send data to a socket server in streaming or batch mode. Each SeaTunnel row is serialized to a JSON object via JsonSerializationSchema and written to the configured TCP port. The connector does not append any delimiter at all — neither a newline, nor any other separator between records. Multiple records therefore travel as one undelimited, continuous TCP byte stream of concatenated JSON objects (for example {"a":1}{"a":2}{"a":3}). The output is explicitly not line-framed JSON, so the peer must handle framing itself: parse consecutive JSON values with a streaming JSON parser (such as Jackson's MappingIterator) rather than a line-oriented parser. Tools like nc -l only echo the raw concatenated bytes, so they are useful for a quick single-row check but cannot split records on their own.

For example, if the data from upstream is [age: 12, name: jared], the content send to socket server is the following: {"name":"jared","age":17}

Sink Options

Name	Type	Required	Default	Description
host	String	Yes		socket server host
port	Integer	Yes		socket server port
max_retries	Integer	No	3	The number of retries to send record failed. Set to `-1` to retry indefinitely, or `0` to fail immediately.
common-options		No	-	Sink plugin common parameters, please refer to Sink Common Options for details

tip

Socket sink is mainly used for local debugging and simple integrations. It reconnects and retries failed writes according to max_retries, but it does not provide exactly-once delivery. The TCP client opens one connection per writer; host/port are the server endpoint that this client connects to.

Task Example

This is randomly generated data written to the Socket side

env {
  parallelism = 1
  job.mode = "STREAMING"
}

source {
  FakeSource {
    plugin_output = "fake"
    schema = {
      fields {
        name = "string"
        age = "int"
      }
    }
  }
}

sink {
  Socket {
    host = "localhost"
    port = 9999
    max_retries = 3
  }
}

Start a port listening

nc -l -v 9999

Start a SeaTunnel task
Socket Server Console print data. No delimiter is appended, so multiple rows arrive as concatenated JSON objects in the raw byte stream (line breaks shown here only for readability):

{"name":"jared","age":17}{"name":"jared","age":18}...

FAQ

Does Socket sink append any delimiter between records?

No. The sink serializes each SeaTunnel row to JSON via JsonSerializationSchema and writes the bytes to the TCP stream with no separator at all — neither \n nor any other character. Multiple records travel as one continuous concatenated byte stream (for example {"a":1}{"a":2}{"a":3}). The peer must therefore use a streaming JSON parser (such as Jackson's MappingIterator), not a line-oriented parser, to split records.

What does `max_retries` control exactly?

max_retries is the number of times the writer retries a failed send after the TCP connection is established (connection refused, broken pipe, write timeouts, etc.). Default is 3. Set it to -1 to retry indefinitely, or 0 to fail the record immediately on the first write failure.

Can several Socket sink writers run in parallel?

Yes. Each writer opens its own TCP connection to host:port, so env.parallelism greater than 1 produces N concurrent connections to the same socket server. Make sure the receiver on the other side is designed to handle multiple clients, otherwise it will only see one client at a time.

Changelog

Change Log

Change	Commit	Version
[improve] socket options (#9517)	https://github.com/apache/seatunnel/commit/af83a302cf	2.3.12
[Feature][Restapi] Allow metrics information to be associated to logical plan nodes (#7786)	https://github.com/apache/seatunnel/commit/6b7c53d03c	2.3.9
[Improve] Remove use `SeaTunnelSink::getConsumedType` method and mark it as deprecated (#5755)	https://github.com/apache/seatunnel/commit/8de7408100	2.3.4
[Improve][build] Give the maven module a human readable name (#4114)	https://github.com/apache/seatunnel/commit/d7cd601051	2.3.1
[Improve][Project] Code format with spotless plugin. (#4101)	https://github.com/apache/seatunnel/commit/a2ab166561	2.3.1
[Feature][Connector] add get source method to all source connector (#3846)	https://github.com/apache/seatunnel/commit/417178fb84	2.3.1
[Hotfix][OptionRule] Fix option rule about all connectors (#3592)	https://github.com/apache/seatunnel/commit/226dc6a119	2.3.0
[Improve][Connector-V2][Socket] Unified exception for socket source & sink connector (#3511)	https://github.com/apache/seatunnel/commit/581292f210	2.3.0
[feature][connector][socket] Add Socket Connector Option Rules (#3317)	https://github.com/apache/seatunnel/commit/b85317bcbe	2.3.0
[Improve][all] change Log to @Slf4j (#3001)	https://github.com/apache/seatunnel/commit/6016100f12	2.3.0-beta
[DEV][Api] Replace SeaTunnelContext with JobContext and remove singleton pattern (#2706)	https://github.com/apache/seatunnel/commit/cbf82f755c	2.2.0-beta
[#2606]Dependency management split (#2630)	https://github.com/apache/seatunnel/commit/fc047be69b	2.2.0-beta
[Feature][Connector-V2] Socket Connector Sink (#2549)	https://github.com/apache/seatunnel/commit/94f4600a4e	2.2.0-beta
[api-draft][Optimize] Optimize module name (#2062)	https://github.com/apache/seatunnel/commit/f79e3112b1	2.2.0-beta

Socket

Support Those Engines​

Key features​

Description​

Sink Options​

Task Example​

FAQ​

Does Socket sink append any delimiter between records?​

What does max_retries control exactly?​

Can several Socket sink writers run in parallel?​

Changelog​