C Open Serial Port
- Nov 04, 2013 open port 21; You have to have a program that is listening on the port for traffic for it to mean anything with it being opened. Normally, port 21 is the FTP port a reserved port. You should not be using any port below 1023.
- Just to be clear for some one who does not know SerialPort behavior the answer above does not use the port.Open which only checks if the CALLER has opened the port, not if say another application has it - for that an attempt to communicate through the port must be made and an exception thrown - port in use, access denied. – Ken May 21 '16 at.
I'm guessing your serial port's FIFO is limited to 16 bytes. Run receive before running send (perhaps you are - I can't tell). Modify receive to read more than one character (suggest 16 characters) at a time. Modify receive to linger after the last character for some small amount of time. Define an end-of-transmission mechanism. Apr 13, 2017 There is an easier way to deal with the serial port. In the toolbox under Componets you can drag a SerialPort component unto your form. Here is a tutorial in C#, should be not too difficult to adapt to C.NET. AFAIK once the port is open it will fire the event when data is available and you need to add the text to your textbox.
-->Definition
Exceptions
Access is denied to the port.
-or-
The current process, or another process on the system, already has the specified COM port open either by a SerialPort instance or in unmanaged code.
One or more of the properties for this instance are invalid. For example, the Parity, DataBits, or Handshake properties are not valid values; the BaudRate is less than or equal to zero; the ReadTimeout or WriteTimeout property is less than zero and is not InfiniteTimeout.
The port name does not begin with 'COM'.
-or-
The file type of the port is not supported.
The port is in an invalid state.
-or- Microsoft office templates ms word.
An attempt to set the state of the underlying port failed. For example, the parameters passed from this SerialPort object were invalid.
The specified port on the current instance of the SerialPort is already open.
Examples
The following code example demonstrates the use of the SerialPort class to allow two users to chat from two separate computers connected by a null modem cable. In this example, the users are prompted for the port settings and a username before chatting. This code example is part of a larger code example provided for the SerialPort class.
Remarks
Only one open connection can exist per SerialPort object.
The best practice for any application is to wait for some amount of time after calling the Close method before attempting to call the Open method, as the port may not be closed instantly.
Security
SecurityPermission
for calling unmanaged code. Associated enumeration: UnmanagedCode Security action: LinkDemand
Applies to
-->Definition
Examples
The following code example demonstrates the use of the SerialPort class to allow two users to chat from two separate computers connected by a null modem cable. In this example, the users are prompted for the port settings and a username before chatting. Both computers must be executing the program to achieve full functionality of this example.
Remarks
Use this class to control a serial port file resource. This class provides synchronous and event-driven I/O, access to pin and break states, and access to serial driver properties. Additionally, the functionality of this class can be wrapped in an internal Stream object, accessible through the BaseStream property, and passed to classes that wrap or use streams.
The SerialPort class supports the following encodings: ASCIIEncoding, UTF8Encoding, UnicodeEncoding, UTF32Encoding, and any encoding defined in mscorlib.dll where the code page is less than 50000 or the code page is 54936. You can use alternate encodings, but you must use the ReadByte or Write method and perform the encoding yourself.
C# Serial Port Tutorial
You use the GetPortNames method to retrieve the valid ports for the current computer.
If a SerialPort object becomes blocked during a read operation, do not abort the thread. Instead, either close the base stream or dispose of the SerialPort object.
C Programming Serial Port
Constructors
| SerialPort()SerialPort()SerialPort()SerialPort() | Initializes a new instance of the SerialPort class. |
| SerialPort(IContainer)SerialPort(IContainer)SerialPort(IContainer)SerialPort(IContainer) | Initializes a new instance of the SerialPort class using the specified IContainer object. |
| SerialPort(String)SerialPort(String)SerialPort(String)SerialPort(String) | Initializes a new instance of the SerialPort class using the specified port name. |
| SerialPort(String, Int32)SerialPort(String, Int32)SerialPort(String, Int32)SerialPort(String, Int32) | Initializes a new instance of the SerialPort class using the specified port name and baud rate. |
| SerialPort(String, Int32, Parity)SerialPort(String, Int32, Parity)SerialPort(String, Int32, Parity)SerialPort(String, Int32, Parity) | Initializes a new instance of the SerialPort class using the specified port name, baud rate, and parity bit. |
| SerialPort(String, Int32, Parity, Int32)SerialPort(String, Int32, Parity, Int32)SerialPort(String, Int32, Parity, Int32)SerialPort(String, Int32, Parity, Int32) | Initializes a new instance of the SerialPort class using the specified port name, baud rate, parity bit, and data bits. |
| SerialPort(String, Int32, Parity, Int32, StopBits)SerialPort(String, Int32, Parity, Int32, StopBits)SerialPort(String, Int32, Parity, Int32, StopBits)SerialPort(String, Int32, Parity, Int32, StopBits) | Initializes a new instance of the SerialPort class using the specified port name, baud rate, parity bit, data bits, and stop bit. |
Fields
| InfiniteTimeoutInfiniteTimeoutInfiniteTimeoutInfiniteTimeout | Indicates that no time-out should occur. |
Properties
| BaseStreamBaseStreamBaseStreamBaseStream | Gets the underlying Stream object for a SerialPort object. |
| BaudRateBaudRateBaudRateBaudRate | Gets or sets the serial baud rate. |
| BreakStateBreakStateBreakStateBreakState | Gets or sets the break signal state. |
| BytesToReadBytesToReadBytesToReadBytesToRead | Gets the number of bytes of data in the receive buffer. |
| BytesToWriteBytesToWriteBytesToWriteBytesToWrite | Gets the number of bytes of data in the send buffer. |
| CanRaiseEventsCanRaiseEventsCanRaiseEventsCanRaiseEvents | Gets a value indicating whether the component can raise an event. (Inherited from Component) |
| CDHoldingCDHoldingCDHoldingCDHolding | Gets the state of the Carrier Detect line for the port. |
| ContainerContainerContainerContainer | Gets the IContainer that contains the Component. (Inherited from Component) |
| CtsHoldingCtsHoldingCtsHoldingCtsHolding | Gets the state of the Clear-to-Send line. |
| DataBitsDataBitsDataBitsDataBits | Gets or sets the standard length of data bits per byte. |
| DesignModeDesignModeDesignModeDesignMode | Gets a value that indicates whether the Component is currently in design mode. (Inherited from Component) |
| DiscardNullDiscardNullDiscardNullDiscardNull | Gets or sets a value indicating whether null bytes are ignored when transmitted between the port and the receive buffer. |
| DsrHoldingDsrHoldingDsrHoldingDsrHolding | Gets the state of the Data Set Ready (DSR) signal. |
| DtrEnableDtrEnableDtrEnableDtrEnable | Gets or sets a value that enables the Data Terminal Ready (DTR) signal during serial communication. |
| EncodingEncodingEncodingEncoding | Gets or sets the byte encoding for pre- and post-transmission conversion of text. |
| EventsEventsEventsEvents | Gets the list of event handlers that are attached to this Component. (Inherited from Component) |
| HandshakeHandshakeHandshakeHandshake | Gets or sets the handshaking protocol for serial port transmission of data using a value from Handshake. |
| IsOpenIsOpenIsOpenIsOpen | Gets a value indicating the open or closed status of the SerialPort object. |
| NewLineNewLineNewLineNewLine | Gets or sets the value used to interpret the end of a call to the ReadLine() and WriteLine(String) methods. |
| ParityParityParityParity | Gets or sets the parity-checking protocol. |
| ParityReplaceParityReplaceParityReplaceParityReplace | Gets or sets the byte that replaces invalid bytes in a data stream when a parity error occurs. |
| PortNamePortNamePortNamePortName | Gets or sets the port for communications, including but not limited to all available COM ports. |
| ReadBufferSizeReadBufferSizeReadBufferSizeReadBufferSize | Gets or sets the size of the SerialPort input buffer. |
| ReadTimeoutReadTimeoutReadTimeoutReadTimeout | Gets or sets the number of milliseconds before a time-out occurs when a read operation does not finish. |
| ReceivedBytesThresholdReceivedBytesThresholdReceivedBytesThresholdReceivedBytesThreshold | Gets or sets the number of bytes in the internal input buffer before a DataReceived event occurs. |
| RtsEnableRtsEnableRtsEnableRtsEnable | Gets or sets a value indicating whether the Request to Send (RTS) signal is enabled during serial communication. |
| SiteSiteSiteSite | Gets or sets the ISite of the Component. (Inherited from Component) |
| StopBitsStopBitsStopBitsStopBits | Gets or sets the standard number of stopbits per byte. |
| WriteBufferSizeWriteBufferSizeWriteBufferSizeWriteBufferSize | Gets or sets the size of the serial port output buffer. |
| WriteTimeoutWriteTimeoutWriteTimeoutWriteTimeout | Gets or sets the number of milliseconds before a time-out occurs when a write operation does not finish. |
Methods
| Close()Close()Close()Close() | Closes the port connection, sets the IsOpen property to |
| CreateObjRef(Type)CreateObjRef(Type)CreateObjRef(Type)CreateObjRef(Type) | Creates an object that contains all the relevant information required to generate a proxy used to communicate with a remote object. (Inherited from MarshalByRefObject) |
| DiscardInBuffer()DiscardInBuffer()DiscardInBuffer()DiscardInBuffer() | Discards data from the serial driver's receive buffer. |
| DiscardOutBuffer()DiscardOutBuffer()DiscardOutBuffer()DiscardOutBuffer() | Discards data from the serial driver's transmit buffer. |
| Dispose()Dispose()Dispose()Dispose() | Releases all resources used by the Component. (Inherited from Component) |
| Dispose(Boolean)Dispose(Boolean)Dispose(Boolean)Dispose(Boolean) | Releases the unmanaged resources used by the SerialPort and optionally releases the managed resources. |
| Equals(Object)Equals(Object)Equals(Object)Equals(Object) | Determines whether the specified object is equal to the current object. (Inherited from Object) |
| GetHashCode()GetHashCode()GetHashCode()GetHashCode() | Serves as the default hash function. (Inherited from Object) |
| GetLifetimeService()GetLifetimeService()GetLifetimeService()GetLifetimeService() | Retrieves the current lifetime service object that controls the lifetime policy for this instance. (Inherited from MarshalByRefObject) |
| GetPortNames()GetPortNames()GetPortNames()GetPortNames() | Gets an array of serial port names for the current computer. |
| GetService(Type)GetService(Type)GetService(Type)GetService(Type) | Returns an object that represents a service provided by the Component or by its Container. (Inherited from Component) |
| GetType()GetType()GetType()GetType() | Gets the Type of the current instance. (Inherited from Object) |
| InitializeLifetimeService()InitializeLifetimeService()InitializeLifetimeService()InitializeLifetimeService() | Obtains a lifetime service object to control the lifetime policy for this instance. (Inherited from MarshalByRefObject) |
| MemberwiseClone()MemberwiseClone()MemberwiseClone()MemberwiseClone() | Creates a shallow copy of the current Object. (Inherited from Object) |
| MemberwiseClone(Boolean)MemberwiseClone(Boolean)MemberwiseClone(Boolean)MemberwiseClone(Boolean) | Creates a shallow copy of the current MarshalByRefObject object. (Inherited from MarshalByRefObject) |
| Open()Open()Open()Open() | Opens a new serial port connection. |
| Read(Byte[], Int32, Int32)Read(Byte[], Int32, Int32)Read(Byte[], Int32, Int32)Read(Byte[], Int32, Int32) | Reads a number of bytes from the SerialPort input buffer and writes those bytes into a byte array at the specified offset. |
| Read(Char[], Int32, Int32)Read(Char[], Int32, Int32)Read(Char[], Int32, Int32)Read(Char[], Int32, Int32) | Reads a number of characters from the SerialPort input buffer and writes them into an array of characters at a given offset. |
| ReadByte()ReadByte()ReadByte()ReadByte() | Synchronously reads one byte from the SerialPort input buffer. |
| ReadChar()ReadChar()ReadChar()ReadChar() | Synchronously reads one character from the SerialPort input buffer. |
| ReadExisting()ReadExisting()ReadExisting()ReadExisting() | Reads all immediately available bytes, based on the encoding, in both the stream and the input buffer of the SerialPort object. |
| ReadLine()ReadLine()ReadLine()ReadLine() | Reads up to the NewLine value in the input buffer. |
| ReadTo(String)ReadTo(String)ReadTo(String)ReadTo(String) | Reads a string up to the specified |
| ToString()ToString()ToString()ToString() | Returns a String containing the name of the Component, if any. This method should not be overridden. (Inherited from Component) |
| Write(Byte[], Int32, Int32)Write(Byte[], Int32, Int32)Write(Byte[], Int32, Int32)Write(Byte[], Int32, Int32) | Writes a specified number of bytes to the serial port using data from a buffer. |
| Write(Char[], Int32, Int32)Write(Char[], Int32, Int32)Write(Char[], Int32, Int32)Write(Char[], Int32, Int32) | Writes a specified number of characters to the serial port using data from a buffer. |
| Write(String)Write(String)Write(String)Write(String) | Writes the specified string to the serial port. |
| WriteLine(String)WriteLine(String)WriteLine(String)WriteLine(String) | Writes the specified string and the NewLine value to the output buffer. |
C++ Serial Port Write
Events
| DataReceivedDataReceivedDataReceivedDataReceived | Indicates that data has been received through a port represented by the SerialPort object. |
| DisposedDisposedDisposedDisposed | Occurs when the component is disposed by a call to the Dispose() method. (Inherited from Component) |
| ErrorReceivedErrorReceivedErrorReceivedErrorReceived | Indicates that an error has occurred with a port represented by a SerialPort object. |
| PinChangedPinChangedPinChangedPinChanged | Indicates that a non-data signal event has occurred on the port represented by the SerialPort object. |
Security
SecurityPermission
for the ability to call unmanaged code. Associated enumeration: UnmanagedCode