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TCP/IP and UDP protocols are specific methods used to send data back and forth from a server to a client computer.
The difference between TCP/IP and UDP is:
With TCP/IP, the handshake means that if one machine sends another some data, the receiving machine sends back a data packet that tells the sending machine the data was received. If the receiving machine requests that the sending machine then confirm that their confirmation packet was received, the sending machine sends a data packet back, and so on.
If the receiving machine receives garbled or otherwise messed up data, it will automatically re-request the data from the sending machine.
UDP is not a handshake protocol... there is no guarantee of data delivery. The data gets sent, and that is it. The receiving machine may or may not successfully receive the data, but the sender doesn't get any confirmation. The programmer has to create the rules for UDP protocol to get responses back from the recipient machine.
open file tcp_ch: name 'tcp://[ip]?[param1=value1]&[param2=value2]&[paramn=valuen]', access outin |
| Example 18-4 TCP/IP Protocol |
|---|
// Very simple TELNET client
line input 'IP address of the telnet server': ip$
open file tcp_ch: name 'tcp://' + ip$ + '?port=23', access outin
print 'Ready for data...'
do
// check for data from the server
// but not forever... just a few iterations
for idx = 1 to 100
line input #tcp_ch: ip$
if ip$ = '' then exit for
ask #tcp_ch, symbol 'data': value rec$
print rec$;
next idx
// check for data from this client
when exception in
key input timeout 1, prompt '': dat$
print #tcp_ch: dat$
use
end when
loop
end
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TCP/IP allows the programmer to transmit data back and forth from one computer to another with the capability of receiving responses and data transmission confirmation.
If an IP address is specified, then it denotes the receive source IP and the send destination IP for a client.
If no IP address is specified, the channel is a server.
The start of the options list begins with a ? (question mark), and each parameter is separated by an & (ampersand). The options are NAMED as outlined in the table below. For example, if you wanted to specify "port 23", you would use:
| Example 18-5 TCP/IP Protocol - Port Parameter |
|---|
open file tcp_ch: name 'tcp://' + '?port=23', access outin |
| Parameter | Description | Default |
|---|---|---|
| Sockets | specifies the number of sockets to use | 100 |
| port | specifies the port number to be used for transmitting data | 31111 |
| ipaddress | the IP address of the CLIENT machine receiving data | none |
| max_receive_queue | specifies the max number of requests able to be received at once | 200 |
| max_send_queue | specifies the max number of requests allowed in the send queue | 200 |
| maxdupconnections | specifies the maximum duplicate connections allowed | 3 |
| timeout | specifies the length of timeout in seconds | 50 |
open file udp_ch: name 'udp://[ip]?[param1=value1]&[param2=value2]&[paramn=valuen]', access outin |
If an IP Address is specified, then it denotes the receive source IP and the send destination IP for a client.
If no IP address is specified, the channel is a server.
The start of the options list begins with a ? (question mark), and each parameter is separated by an & (ampersand). The options are NAMED as outlined in the table below. For example, if you wanted to specify a "timeout of 20 seconds", you would use:
open file udp_ch: name 'udp://' + '?timeout=20', access outin |
| Parameter | Description | Default |
|---|---|---|
| Sockets | specifies the number of sockets to use | 100 |
| port | specifies the port number to be used for transmitting data | 31111 |
| ipaddress | the IP address of the CLIENT machine receiving data | none |
| max_receive_queue | specifies the max number of requests able to be received at once | 200 |
| max_send_queue | specifies the max number of requests allowed in the send queue | 200 |
| maxdupconnections | specifies the maximum duplicate connections allowed | 3 |
| timeout | specifies the length of timeout in seconds | 50 |
open #n: name "com://port=p?options", access outin |
The example below is not a 'runnable' example. It is intended only to illustrate how to use the communication support in Sheerpower.
| Example 18-6 Communication Port |
|---|
// use com4 port for talking to some device open file com_ch: name 'com://port=4', access outin print #com_ch: 'AT' line input #com_ch: cdata$ if cdata$ <> '' then print 'Response was: '; cdata$ end |
Communication (COM) Port Support is available to access the serial communication ports on a computer.
The port number p is required. i.e., 1, 2, 3, etc.
The start of the options list begins with a ? (question mark), and each parameter is separated by an & (ampersand). The options are NAMED as outlined in the table below. For example, if you wanted to specify "7-bits", you would use:
| Example 18-7 Communication Port |
|---|
com://port=4?speed=9600&bits=7 |
| Option | Description | Default | Value |
|---|---|---|---|
| SPEED | specifies baud rate | 9600 | 110, 300, 600, 1200, 2400, 4800, 9600, 14400, 19200, 38400, 56000, 128000, 256000 |
| BITS | specifies number of bits | 8 | 5, 6, 7, 8 |
| PARITY | specifies parity used | off | off, even, odd, mark, space |
| STOPBITS | specifies number of stop bits | 1 | 1, 1.5, 2 |
| DSRDTR | specifies dsr/dtr protocol | off | on, off |
| RTSCTS | specifies rts/cts protocol | off | on, off |
| XONXOFF | specifies xon/xoff protocol | off | on, off |
If the baud or bit value is invalid, the default value is used.
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