Скачать или смотреть Solving TCP/IP Socket Data Reception Issues: Why Am I Receiving a Random Large Number?

Discover the solutions to common errors when receiving data in a client-server TCP/IP application. Learn how to debug socket communication issues with practical examples in C+ + .
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This video is based on the question https://stackoverflow.com/q/63437314/ asked by the user 'Robert-Nicolae Solca' ( https://stackoverflow.com/u/11874799/ ) and on the answer https://stackoverflow.com/a/63437516/ provided by the user 'Joni' ( https://stackoverflow.com/u/318758/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding the Problem in TCP/IP Socket Communication

Building a client-server application in C+ + using TCP/IP sockets can sometimes present unexpected challenges. One common issue developers face is receiving unexplained or random large numbers instead of the expected data.

For instance, you might establish a connection between your client and server, send a message, and then witness your client receiving a number that doesn't correspond to any message sent from the server. This can leave you scratching your head, as you are trying to determine the root cause of the problem.

In this post, we will break down your code to analyze the potential culprits behind this frustrating behavior and provide actionable solutions to correct the errors.

The Scenario Breakdown

In the given setup, you have:

A server that receives a username from the client and responds with the server's name and the user's role.

A client that sends a username and expects to receive the corresponding server name and user role.

You received the following logs indicating unusual behavior:

Server Log:

[[See Video to Reveal this Text or Code Snippet]]

Client Log:

[[See Video to Reveal this Text or Code Snippet]]

This indicates that instead of the expected role, a large value is received.

Analyzing the Code

The send_message Function

In the send_message function, you are currently using:

[[See Video to Reveal this Text or Code Snippet]]

Issue: Using sizeof(message_left.c_str()) retrieves the size of the pointer, not the actual size of the message.

The Correct Approach

You should amend this to:

[[See Video to Reveal this Text or Code Snippet]]

The recv_message Function

In this function, you are using:

[[See Video to Reveal this Text or Code Snippet]]

Issue: You need to correctly check the return value of recv, which can be -1 for an error.

The Correct Approach

Modify it to:

[[See Video to Reveal this Text or Code Snippet]]

The get_message Function

In the get_message method, the size of data being read should also handle the possibility of receiving negative values:

[[See Video to Reveal this Text or Code Snippet]]

Issue: len should be defined as ssize_t.

The Correct Approach

Change it to:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

These minor adjustments in your code should rectify the issue of receiving random large numbers when communicating between the client and server. Properly handling sizes and return values is crucial in socket programming.

By implementing these changes, you can ensure that data sent over TCP/IP sockets is accurately received, leading to a smoother, more reliable application.

Whether you are new to networking in C+ + or looking to troubleshoot existing applications, paying attention to data types, return values, and sizes can save a lot of headaches down the road.

Keep coding, and don't let socket issues disrupt your journey!