Verify API Connection

A user can verify whether their API session is connected at any point with the EClient.isConnected() function.

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print(app.isConnected())

eConnect starts by requesting from the operating system that a TCP socket be opened to the specified IP address and socket port. If the socket cannot be opened, the operating system (not TWS) returns an error which is received by the API client as error code 502 to IBApi.EWrapper.error (Note: since this error is not generated by TWS it is not captured in TWS log files). Most commonly error 502 will indicate that TWS is not running with the API enabled, or it is listening for connections on a different socket port. If connecting across a network, the error can also occur if there is a firewall or antivirus program blocking connections, or if the router’s IP address is not listed in the “Trusted IPs” in TWS.

After the socket has been opened, there must be an initial handshake in which information is exchanged about the supported version of the TWS and API to ensure each platform can interpret received messages correctly.

• For this reason it is important that the main EReader object is not created until after a connection has been established. The initial connection results in a negotiated common version between TWS and the API client which will be needed by the EReader thread in interpreting subsequent messages.

After the highest version number which can be used for communication is established, TWS will return certain pieces of data that correspond specifically to the logged-in TWS user’s session. This includes (1) the account number(s) accessible in this TWS session, (2) the next valid order identifier (ID), and (3) the time of connection. In the most common mode of operation the EClient.AsyncEConnect field is set to false and the initial handshake is taken to completion immediately after the socket connection is established. TWS will then immediately provides the API client with this information.

• Important: The IBApi.EWrapper.nextValidID callback is commonly used to indicate that the connection is completed and other messages can be sent from the API client to TWS. There is the possibility that function calls made prior to this time could be dropped by TWS.

There is an alternative, deprecated mode of connection used in special cases in which the variable AsyncEconnect is set to true, and the call to startAPI is only called from the connectAck() function. All IB samples use the mode AsyncEconnect = False.