BOOL ReadLine(
	LPTSTR lpszBuffer,
	LPINT lpnLength
);

BOOL ReadLine(
	LPTSTR lpszBuffer,
	INT nMaxLength
);

BOOL ReadLine(
	CString& strBuffer,
	INT nMaxLength
);

The ReadLine method reads up to a line of data from the server and returns it in a string buffer.

Parameters

lpszBuffer

Pointer to the string buffer that will contain the data when the method returns. The string will be terminated with a null character, and will not contain the end-of-line characters. An alternate form of the method accepts a CString argument which will contain the line of text returned by the server.

lpnLength

A pointer to an integer value which specifies the length of the buffer. The value should be initialized to the maximum number of characters that can be copied into the string buffer, including the terminating null character. When the method returns, its value will updated with the actual length of the string.

nMaxLength

An integer value which specifies the maximum length of the buffer.

Return Value

If the method succeeds, the return value is non-zero. If the method fails, the return value is zero. To get extended error information, call GetLastError.

Remarks

The ReadLine method reads data from the server and copies into a specified string buffer. Unlike the Read method which reads arbitrary bytes of data, this method is specifically designed to return a single line of text data in a string. When an end-of-line character sequence is encountered, the method will stop and return the data up to that point. The string buffer is guaranteed to be null-terminated and will not contain the end-of-line characters.

There are some limitations when using ReadLine. The method should only be used to read text, never binary data. In particular, the method will discard nulls, linefeed and carriage return control characters. The Unicode version of this method will return a Unicode string, however it does not support reading raw Unicode data from the socket. Any data read from the socket is internally buffered as octets (eight-bit bytes) and converted to Unicode using the MultiByteToWideChar function.

This method will force the thread to block until an end-of-line character sequence is processed, the read operation times out or the server closes its end of the socket connection. If this method is called with asynchronous events enabled, it will automatically switch the socket into a blocking mode, read the data and then restore the socket to asynchronous operation. If another socket operation is attempted while ReadLine is blocked waiting for data from the server, an error will occur. It is recommended that this method only be used with blocking (synchronous) socket connections; if the application needs to establish multiple simultaneous connections, it should create worker threads to manage each connection.

The Read and ReadLine method calls can be intermixed, however be aware that Read will consume any data that has already been buffered by the ReadLine method and this may have unexpected results.

Unlike the Read method, it is possible for data to be returned in the string buffer even if the return value is zero. Applications should check the length of the string to determine if any data was copied into the buffer. For example, if a timeout occurs while the method is waiting for more data to arrive on the socket, it will return zero; however, data may have already been copied into the string buffer prior to the error condition. It is the responsibility of the application to process that data, regardless of the return value.

Example

CString strBuffer;
BOOL bResult;

do
{
    bResult = pClient->ReadLine(strBuffer);

    if (strBuffer.GetLength() > 0)
    {
        // Process the line of data returned in the string
        // buffer; the string is always null-terminated
    }
} while (bResult);

DWORD dwError = pClient->GetLastError();

if (dwError == ST_ERROR_CONNECTION_CLOSED)
{
    // The server has closed its side of the connection and
    // there is no more data available to be read
}
else if (dwError != 0)
{
    // An error has occurred while reading a line of data
}

Requirements

Minimum Desktop Platform: Windows 7 Service Pack 1
Minimum Server Platform: Windows Server 2008 R2 Service Pack 1
Header File: cstools11.h
Import Library: cstshv11.lib
Unicode: Implemented as Unicode and ANSI versions

See Also

IsReadable, Peek, Read, Write, WriteLine

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