如何在C#中解析GSM调制解调器接收的SMS短信内容？

Hey there! Let's break down how to filter out irrelevant modem responses and extract the key SMS details (sender number, timestamp, message content) from the +CMT lines you're receiving.

Step 1: Filter Out Irrelevant Responses #

First, you need to sift through all incoming serial data and ignore lines that don't relate to incoming SMS. That means skipping:

• AT command echoes (like AT+CMGF=1 or AT+CNMI=1,2,0,0,0)
• Success/error acknowledgments (like OK)
• Any other lines that don't start with +CMT:

In your SerialDataReceivedEventHandler method, read the incoming data line by line, and only process lines that match the +CMT: prefix.

Step 2: Parse the +CMT Line for Sender & Timestamp #

The +CMT line follows a standard GSM format, which makes parsing straightforward. Let's use your example:

+CMT: "+xxxxxxxxxx",,"18/05/30,10:08:08+18"

Option 1: String Splitting (Simple Approach) #

You can split the line using basic string operations to extract values:

// Example line from modem
string cmtLine = "+CMT: \"+xxxxxxxxxx\",,\"18/05/30,10:08:08+18\"";

// Remove the "+CMT: " prefix
string contentPart = cmtLine.Substring(6).Trim();

// Split by the quoted separator to avoid breaking on commas inside values
string[] parts = contentPart.Split(new[] { "\",," }, StringSplitOptions.None);
string senderNumber = parts[0].Trim('"');
string timestampStr = parts[1].Trim('"');

Option 2: Regular Expression (More Robust) #

For better handling of minor format variations, use a regex pattern to capture the sender and timestamp reliably:

using System.Text.RegularExpressions;
using System.Globalization;

string cmtPattern = @"\+CMT: ""(\+?\d+)"",,""(\d{2}/\d{2}/\d{2},\d{2}:\d{2}:\d{2}\+\d{2})""";
Match match = Regex.Match(cmtLine, cmtPattern);

if (match.Success)
{
    string senderNumber = match.Groups[1].Value;
    string timestampStr = match.Groups[2].Value;
    // Convert timestamp to a DateTime object for database storage
    DateTime smsTimestamp = DateTime.ParseExact(timestampStr, "dd/MM/yy,HH:mm:sszzz", CultureInfo.InvariantCulture);
}

Step 3: Extract the SMS Content #

Right after the +CMT line, the next line(s) contain the actual SMS message content (like your example's Testing).

In your serial data handling, after identifying a +CMT line, read subsequent lines until you hit a non-content line (like another command response or the end of the data stream). Note that longer SMS might span multiple lines, so concatenate those lines if needed.

Step 4: Store to Database #

Once you have the sender number, parsed timestamp, and message content, insert them into your database using your preferred data access method (EF Core, ADO.NET, etc.). Here's a quick pseudocode example:

// Pseudocode for database insertion
using (var db = new MessengerDbContext())
{
    var incomingSms = new IncomingSms
    {
        SenderNumber = senderNumber,
        ReceivedAt = smsTimestamp,
        Content = messageContent
    };
    db.IncomingSms.Add(incomingSms);
    db.SaveChanges();
}

Key Notes #

• Handle encoding: GSM modems often use GSM 03.38 encoding for messages, so you may need to convert incoming text to UTF-8 if your database uses that standard.
• Edge cases: Watch for empty messages, messages with special characters, or slight timestamp format variations (some modems might use different time zone notations).

内容的提问来源于stack exchange，提问作者Daniel Žeimo