3 Troubleshooting TCP/IP Connection Problems

Establishing a TCP/IP connection between a SequeLink Client and a SequeLink service consists of the following steps.

A low-level TCP/IP connection is made from a SequeLink Client to a SequeLink Server that is listening on the specified TCP/IP port. See the following section "Establishing a TCP/IP Connection" for more information.

When this low-level TCP/IP connection has been established, the SequeLink Client exchanges operational parameters, or a handshake, with the SequeLink service. See "Connection Handshaking" for more information.

This chapter describes situations that may cause TCP/IP connections between a SequeLink Client and a SequeLink service to fail. See Chapter 5 "Error Messages" for information about the error codes referenced.

Establishing a TCP/IP Connection

If you are experiencing problems when a TCP/IP connection is made to a SequeLink Server, follow these recommendations:

If the server host is specified by a symbolic host name instead of an IP formatted address, make sure that the host name can be mapped to an IP address. Error 2469 indicates that the specified server could not map the server host name to an IP address.

Other TCP/IP applications, such as ping, telnet, ftp, or traceroute, should return similar errors.

Confirm that it is possible to make a TCP/IP connection with the specified server host using other TCP/IP applications, such as ping, telnet, ftp, or traceroute, if the requested service is available on that host. If other TCP/IP applications can connect to the server host, look for the following problems in SequeLink:

An invalid IP address has been specified.

An invalid host name has been specified, even if the host name is mapped to a valid IP address.

The server host may not be operational.

The server host could not be reached from the client machine because of a routing problem.

If a time limit is set on the connection, check whether a timeout occurred. Error 2320 is returned when TCP/IP cannot connect to the server host within the specified time. Increase the time interval and try again to connect.

If the port is specified by a name instead of a number, check whether the name can be mapped to a port number. Error 2470 is returned if the specified name cannot be mapped to a port number. Check the TCP/IP services configuration file.

Verify that a SequeLink service is listening on the server host at the specified port. Use the netstat -a command on the host to obtain a list of TCP ports that are in the listening state.

Check for congestion problems on the server. Error 2306 or Error 2308 is returned if TCP/IP can reach the server and a service is listening on the server host at the specified port, but too many TCP/IP connection attempts are being made simultaneously for the server to handle.

Connection Handshaking

If you are experiencing problems during handshaking after the low-level TCP/IP connection has been made to a SequeLink Server, follow these recommendations:

You may have specified a TCP/IP port that is not used by a SequeLink service.

If the specified port is serviced by a SequeLink Server of an earlier, incompatible version (SequeLink 4.x), the following errors can occur:

Error 2200. The client did not receive a reply from the server within the specified time frame. This error occurs only if a connection timeout is specified.

Error 2300. The server closed the transport connection.

If the specified port is serviced by a server that is not a SequeLink server, the following errors can occur:

Error 2200. The client did not receive a reply from the server within the specified time frame. This error occurs only if a connection timeout is specified.

Error 2300. The server closed the transport connection.

Error 2310. The server went down while trying to process the handshake request. The connection was closed.

Error 2315. The server received the handshake request and returned a non-IIOP reply that the client could not understand.

You may be connecting with a previous, incompatible version of the SequeLink Client (SequeLink 4.x) to a SequeLink 5.5 Server:

The client receives an error message that informs you that the server has closed the connection during the initial handshake.

If the specified port is serviced by a SequeLink 5.5 Server, the following errors can occur:

Error 2200. The client did not receive a reply from the server within the specified time frame. This error occurs only if a connection timeout is specified.

Error 2312. A connection was established with the server, but no data was received on the server within the keep alive period. Increase the keep alive setting on the server.