TCP/IP Ports and Sockets Explained

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Furthermore, it also supports data verification, expire-time verification, UDP, binary protocol, facebook test, replication test, multi-get and reconnection, etc. Memslap manages network connections like memcached with libevent. Each thread of memslap is bound with a CPU core, all the threads don't communicate with each other, and there are several socket connections in each thread. Each connection keeps key size distribution, value size distribution, and command distribution by itself.

All the network events are managed by libevent as memcached. The network module of memslap is similar to memcached. Libevent can ensure memslap can handle network very efficiently. Memslap has the similar implementation of multi-threads to memcached. Memslap creates one or more self-governed threads; each thread is bound with one CPU core if the system supports setting CPU core affinity.

In addition, each thread has a libevent to manage the events of the network; each thread has one or more self-governed concurrencies; and each concurrency has one or more socket connections. Memslap can create thousands of socket connections, and each concurrency has tens of socket connections. Each concurrency randomly or sequentially selects one socket connection from its socket connection pool to run, so memslap can ensure each concurrency handles one socket connection at any given time.

Users can specify the number of concurrency and socket connections of each concurrency according to their expected workload. In order to improve time efficiency and space efficiency, memslap creates a random characters table with 10M characters. All the suffixes of keys and values are generated from this random characters table.

Memslap uses the offset in the character table and the length of the string to identify a string. It can save much memory. Each key contains two parts, a prefix and a suffix. In order to verify the data set before, memslap need to ensure each key is unique, so it uses the prefix to identify a key. And memslap has an algorithm to ensure that. It only generates enough objects to fill the task window default 10K objects of each concurrency. Each object has the following basic information, key prefix, key suffix offset in the character table, key length, value offset in the character table, and value length.

In the work process, each concurrency sequentially or randomly selects an object from the window to do set operation useful implementation of multi-servers udp tcp multi-get and binary protocol get operation. At the same time, each concurrency kicks objects out of its window and adds new object into it. Memslap uses libevent to schedule all the concurrencies of threads, and each concurrency schedules tasks based on the local task window.

Memslap assumes that if each concurrency keeps the same key distribution, value distribution and commands distribution, from outside, memslap keeps all the distribution as a whole.

Each task window includes a lot of objects, each object stores its basic information, such as key, value, expire time, and so useful implementation of multi-servers udp tcp multi-get and binary protocol. At any time, all the objects in the window keep the same and fixed key and value distribution. If an object is overwritten, the value of the object will be updated.

Memslap verifies the data or expire-time according to the object information stored in the task window. Libevent selects which concurrency to handle based on a specific network event. Then the concurrency selects which command get or set to operate based on the command distribution. If it needs to kick out an old object and useful implementation of multi-servers udp tcp multi-get and binary protocol a new object, in order to keep the same key and value distribution, the new object must have the same key length and value length.

If memcached server has two cache layers memory and SSDrunning memslap with different window sizes can get different cache miss rates. If memslap adds enough objects into the windows at the beginning, and the cache of memcached cannot store all the objects initialized, then memslap will get some objects from the second cache layer. It causes the first cache layer to miss.

So the user can specify the window size to get the expected miss rate of the first cache layer. Because each thread is self-governed, memslap can assign different threads to handle different memcached servers. This is just one of the ways in which memslap supports multiple servers.

The only limitation is that the number of servers cannot be greater than the number of threads. The other way to support multiple servers is for replication test. Each concurrency has one socket connection to each memcached server.

For the implementation, memslap can set some objects to one memcached server, and get these objects from the other servers. By default, Memslap does single get. If the user specifies multi-get option, memslap will collect enough get commands and pack and send the commands together. Because UDP is unreliable, dropped packages and out-of-order packages may occur.

Memslap creates a memory buffer to handle these problems. Memslap tries to read all the response data of one command from the server and reorders the response data. If some packages get lost, the waiting timeout mechanism can ensure half-baked packages will be discarded and the next command will be sent.

The user must specify one server at least to run memslap. The rest of the parameters have default values, as shown below:. The minimum key size is 16 bytes; the maximum key size is bytes.

The precision of proportion is 0. The proportion of distribution will be rounded to 3 decimal places. The minimum value size is 1 bytes; the maximum value size is 1M bytes.

Currently, memslap only supports set and get commands. The high performance of memslap benefits from the special schedule of thread and concurrency. The default number of threads is 1; the default number of concurrency is If the system supports setting CPU affinity and the number of threads specified by the user is greater than 1, memslap will try to bind each thread to a different CPU core. So if you want to get the best performance memslap, it is better to specify the number of thread equal to the number of CPU cores.

The number of threads specified by the user can also be less or greater than the number of CPU cores. Because of the limitation of implementation, the number of concurrencies could be the multiple of the number of threads. The memslap performs very well, when used to test the performance of memcached servers.

Most of the time, the bottleneck is the network or the server. If for some reason the user wants to limit the performance of memslap, there are two ways to do this:. Decrease the number of threads and concurrencies. This option allows the user to get the expected throughput. Most of the time, the user does not need useful implementation of multi-servers udp tcp multi-get and binary protocol specify the window size.

The default window size is 10k. For Schooner Memcached, the user can specify different window sizes to get different cache miss rates based on the test case. If you use this utility to test the performance of Schooner Memcached, you can specify a proper window size to get the expected cache miss rate.

The formula for calculating window size is as follows:. Memslap supports both data verification and expire-time verification. Specify the "--verbose" options to get more detailed error information. If the objects are gotten, memslap will verify the expire-time and value.

Memslap supports multi-servers based on self-governed thread. There is a limitation that the number of servers cannot be greater than the number of threads. Memslap assigns one thread to handle one server at least.

The above command means that there are 6 threads, with each thread having 6 concurrencies and that threads 0 and 3 handle server 0 The user can start up several memslap instances.

The user can run memslap on different client machines to communicate with the same memcached server at the same. It is recommended that the user start different memslap on different machines using the same configuration.

The default memslap runs with time mode. The default run time is 10 minutes. If it times out, memslap will exit. Do not useful implementation of multi-servers udp tcp multi-get and binary protocol both execute number mode and time mode at the same time; just specify one instead. Memslap will dump the statistics of the commands get and set at the frequency of every 20 seconds. Memslap by default does single get with TCP. Memslap also supports data verification and expire-time verification for multi-get.

Because of the different implementation of the ASCII protocol and binary protocol, there are some differences between the two. For TCP, memslap does not reconnect the memcached server if socket connections are lost. If all the socket connections are lost or memcached server crashes, memslap will exit.

UDP is not supported by the binary protocol because the binary protocol of memcached does not support that. The above command means that memslap will do facebook test, each concurrency has socket TCP connections and one UDP socket. For replication test, the user must specify at least two memcached servers.

The above command means that there are 2 replication memcached servers, memslap will set objects to both server 0 and server 1, get objects which are set to server useful implementation of multi-servers udp tcp multi-get and binary protocol before from server 1, and also get objects which are set to server useful implementation of multi-servers udp tcp multi-get and binary protocol before from server 0.

If server 0 crashes, memslap will only get objects from server 1. If server 0 comes back to life again, memslap will reconnect server 0. If both server 0 and server 1 crash, memslap will exit.

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WebSocket is a computer communications protocol , providing full-duplex communication channels over a single TCP connection. The WebSocket protocol enables interaction between a web client such as a browser and a web server with lower overheads, facilitating real-time data transfer from and to the server.

This is made possible by providing a standardized way for the server to send content to the client without being first requested by the client, and allowing messages to be passed back and forth while keeping the connection open. In this way, a two-way ongoing conversation can take place between the client and the server. The communications are done over TCP port number 80 or in the case of TLS -encrypted connections , which is of benefit for those environments which block non-web Internet connections using a firewall.

Similar two-way browser-server communications have been achieved in non-standardized ways using stopgap technologies such as Comet. WebSocket also requires web applications on the server to support it. TCP alone deals with streams of bytes with no inherent concept of a message. Before WebSocket, port 80 full-duplex communication was attainable using Comet channels; however, Comet implementation is nontrivial, and due to the TCP handshake and HTTP header overhead, it is inefficient for small messages.

The WebSocket protocol aims to solve these problems without compromising security assumptions of the web. The WebSocket protocol specification defines ws WebSocket and wss WebSocket Secure as two new uniform resource identifier URI schemes [4] that are used for unencrypted and encrypted connections, respectively.

Apart from the scheme name and fragment is not supported , the rest of the URI components are defined to use URI generic syntax. Using browser developer tools, developers can inspect the WebSocket handshake as well as the WebSocket frames. After the protocol was shipped and enabled by default in multiple browsers, the RFC was finalized under Ian Fette in December An older, less secure version of the protocol was implemented in Opera 11 and Safari 5, as well as the mobile version of Safari in iOS 4.

To establish a WebSocket connection, the client sends a WebSocket handshake request, for which the server returns a WebSocket handshake response, as shown in the example below. Once the connection is established, communication switches to a bidirectional binary protocol which doesn't conform to the HTTP protocol. In addition to Upgrade headers, the client sends a Sec-WebSocket-Key header containing base64 -encoded random bytes, and the server replies with a hash of the key in the Sec-WebSocket-Accept header.

This is intended to prevent a caching proxy from re-sending a previous WebSocket conversation, [31] and does not provide any authentication, privacy or integrity. Once the connection is established, the client and server can send WebSocket data or text frames back and forth in full-duplex mode. The data is minimally framed, with a small header followed by payload.

WebSocket transmissions are described as "messages", where a single message can optionally be split across several data frames. This can allow for sending of messages where initial data is available but the complete length of the message is unknown it sends one data frame after another until the end is reached and marked with the FIN bit. With extensions to the protocol, this can also be used for multiplexing several streams simultaneously for instance to avoid monopolizing use of a socket for a single large payload.

It is important from a security perspective to validate the "Origin" header during the connection establishment process on the server side against the expected origins to avoid Cross-Site WebSocket Hijacking attacks, which might be possible when the connection is authenticated with Cookies or HTTP authentication.

It is better to use tokens or similar protection mechanisms to authenticate the WebSocket connection when sensitive private data is being transferred over the WebSocket. WebSocket protocol client implementations try to detect if the user agent is configured to use a proxy when connecting to destination host and port and, if it is, uses HTTP CONNECT method to set up a persistent tunnel. The WebSocket protocol defines a ws: Some proxy servers are transparent and work fine with WebSocket; others will prevent WebSocket from working correctly, causing the connection to fail.

In some cases, additional proxy server configuration may be required, and certain proxy servers may need to be upgraded to support WebSocket. If unencrypted WebSocket traffic flows through an explicit or a transparent proxy server without WebSockets support, the connection will likely fail. However, since the wire traffic is encrypted, intermediate transparent proxy servers may simply allow the encrypted traffic through, so there is a much better chance that the WebSocket connection will succeed if WebSocket Secure is used.

Using encryption is not free of resource cost, but often provides the highest success rate since it would be travelling through a secure tunnel. A mid draft version hixie broke compatibility with reverse proxies and gateways by including eight bytes of key data after the headers, but not advertising that data in a Content-Length: More recent drafts e.

From Wikipedia, the free encyclopedia. Internet Assigned Numbers Authority. Retrieved 7 April Archived from the original on June 10, Retrieved 8 July Archived from the original on Update WebSocket protocol to hybi".

Retrieved 25 July Web Application Security Blog. Internet Engineering Task Force. The WebSocket protocol, draft hybi Retrieved June 15, Television and video game console. Software no longer in development shown in italics Category Commons Internet portal Software portal.

Retrieved from " https: Pages using div col with deprecated parameters Pages using RFC magic links. Views Read Edit View history. This page was last edited on 22 March , at By using this site, you agree to the Terms of Use and Privacy Policy. Television and video game console Gecko -based Kylo.