Samplers in JMeter allows JMeter to send different types of requests to a server. Samplers are the actual requests, JMeter sends to the web server under test.

Each sampler (except Test Action) generates one or more sample results. The sample results have various attributes (success/fail, elapsed time, data size etc.) and can be viewed in the various listeners. Some important Samplers available are as follows:

• FTP Request
• HTTP Request
• Java Request
• SMTP Sampler
• BSF Sampler
• JDBC Request
• SOAP/XML RPC-Request

Complete list of available samplers can be seen in the following figure:

Let’s have a look on some of the common Samplers:

1:  HTTP Request

HTTP Request Sampler is used to send HTTP/HTTPS requests to the web server.

1. Enter Domain name / IP address of the web server. Do not include the “http://” prefix.
2. Enter Path to resource.

Note: If you are going to send multiple requests to the same web server, consider using an HTTP Request Defaults Configuration Element so you do not have to enter the same information for each HTTP Request. Or, instead of manually adding HTTP Requests, you may want to use JMeter's HTTP(S) Test Script Recorder to create them. This can save you time if you have a lot of HTTP requests or requests with many parameters.

2:  FTP Request

FTP Request Sampler allows to send an FTP "retrieve/download file" or "upload file" request to an FTP server.

1. Domain name / IP address of FTP server.
2. File name to retrieve
3. Select if you want to download a file
4. Select if you want to upload a file
5. Credentials of FTP account User

Note: If you are going to send multiple requests to the same FTP server, consider using a FTP Request Defaults Configuration Element so you do not have to enter the same information for each FTP Request Generative Controller. When downloading a file, it can be stored on disk (Local File) or in the Response Data, or both.

3:  JDBC Request

JDBC Request Sampler is useful for database testing. It sends JDBC request consist of SQL query to a database.

1. Variable Name that the connection pool is bound to. The variable name   should be same as of the 'Variable Name' defined in a JDBC Connection Configuration.
2. Select an appropriate query type from dropdown
3. Write your SQL query without semicolon (;)
4. Enter values to update (comma-separated)
5. Enter columns data types (comma-separated)

4:  SMTP Sampler

SMTP Sampler is used to test a Mail Server where it sends email messages by using SMTP/SMTPS protocol.

1. Server settings to set Mail Server Name and Port
2. Mail settings to send an email
3. Authentication Settings
4. Security settings
5. Message settings to enter Subject, Message Body and attach any file