The Internet protocol suite supports a connectionless transmission protocol, which is called User Datagram Protocol (UDP). UDP provides a way for applications to send encapsulated IP packets without establishing a connection. RFC 768 describes UDP. The transport layer of the Internet has two main protocols that complement each other. The connectionless one is UDP, which does nothing special except for sending data packets to applications and allowing them to construct their own protocols at the required level. The connection-oriented one is TCP, which does almost everything.
1.Introduction to the Agreement
UDP is the abbreviation of User Datagram Protocol. The Chinese name is User Datagram Protocol. It is a connectionless transport layer protocol in the OSI (Open System Interconnection) reference model. It provides transaction-oriented simple and unreliable information transmission services. , IETF RFC 768 is the official specification of UDP. The protocol number of UDP in IP packets is 17.
The UDP protocol is used to process data packets the same as the TCP protocol. In the OSI model, both are located in the transport layer, which is the upper layer of the IP protocol. UDP has the disadvantages of not providing data packet grouping, assembly, and inability to sort data packets. That is to say, after the message is sent, it is impossible to know whether it has arrived safely and completely. UDP is used to support network applications that need to transfer data between computers. Numerous client/server network applications including network video conferencing systems need to use the UDP protocol. The UDP protocol has been used for many years since its inception. Although its initial brilliance has been concealed by some similar protocols, even today UDP is still a very practical and feasible network transport layer protocol.
Many applications only support UDP, such as multimedia data streams, do not generate any additional data, and do not retransmit even if it knows that there is a damaged packet. When emphasizing transmission performance rather than transmission integrity, such as audio and multimedia applications, UDP is the best choice. UDP is also a good choice when the data transmission time is so short that the previous connection process has become the main body of the entire traffic.
(1) Content
UDP is a connectionless transport layer protocol in the OSI reference model. It is mainly used in transmissions that do not require the order of packets to arrive. The inspection and sorting of the packet transmission order is done by the application layer [4], providing simple and unreliable transaction-oriented Information delivery service. The UDP protocol is basically the interface between the IP protocol and the upper layer protocol. The UDP protocol applies to multiple applications running on the same device.
UDP provides connectionless communication and does not guarantee the reliability of transmitted data packets. It is suitable for transmitting a small amount of data at a time. The reliability of UDP transmission is the responsibility of the application layer. Commonly used UDP port numbers are: 53 (DNS), 69 (TFTP), and 161 (SNMP). The UDP protocols used include: TFTP, SNMP, NFS, DNS, BOOTP.
UDP packets do not have reliability guarantees, sequence guarantees, and flow control fields, and their reliability is poor. However, because the UDP protocol has fewer control options, the delay in the data transmission process is small, and the data transmission efficiency is high. It is suitable for applications that do not require high reliability, or applications that can guarantee reliability, such as DNS, TFTP, and SNMP Wait.
(2) Function
In order to identify multiple destination addresses on a given host, while allowing multiple applications to work on the same host and independently send and receive data packets, the user datagram protocol UDP is designed.
UDP uses the underlying Internet protocol to transmit messages, and provides unreliable connectionless data packet transmission services like IP. It does not provide functions such as message arrival confirmation, sequencing, and flow control.
UDP Helper can realize the relay and forwarding of broadcast messages on the designated UDP port, that is, convert the broadcast messages on the designated UDP port into unicast messages and send them to the designated server, playing the role of relay.
2.Message format
In the UDP protocol hierarchy model, UDP is located above the IP layer. The application program accesses the UDP layer and then uses the IP layer to transmit datagrams. The data part of the IP data packet is the UDP datagram. The IP layer header specifies the source host and destination host address, while the UDP layer header specifies the source port and destination port on the host. The segment of UDP transmission consists of an 8-byte header and payload field.
The UDP header consists of 4 fields, each of which occupies 2 bytes, including the source port number, destination port number, packet length, and check value.
(1) Port number
The UDP protocol uses port numbers to reserve their own data transmission channels for different applications. UDP and TCP protocols use this mechanism to support multiple applications sending and receiving data at the same time. The data sender (can be client or server) sends UDP packets out through the source port, and the data receiver receives data through the destination port. Some network applications can only use static ports reserved or registered for them in advance; while other network applications can use unregistered dynamic ports. Because the UDP header uses two bytes to store the port number, the valid range of the port number is from 0 to 65535. Generally speaking, port numbers greater than 49151 represent dynamic ports. There are two ways to specify the UDP port number: the port specified by the management organization and the way of dynamic binding.
(2) Length
The length of a datagram refers to the total number of bytes including the header and the data part. Because the length of the header is fixed, this field is mainly used to calculate the variable-length data part (also known as the data load). The maximum length of the datagram varies depending on the operating environment. Theoretically, the maximum length of a datagram including the header is 65535 bytes. However, some practical applications often limit the size of the datagram, sometimes reducing it to 8192 bytes.
(3) Check value
The UDP protocol uses the check value in the header to ensure data security. The check value is first calculated by a special algorithm at the data sender, and needs to be recalculated after being transmitted to the receiver. If a datagram is tampered with by a third party during transmission or damaged due to line noise or other reasons, the sender and receiver's check calculation value will not match, so the UDP protocol can detect whether there is an error. This is different from the TCP protocol, which requires a check value.
Many link layer protocols provide error checking, including the popular Ethernet protocol. Maybe you want to know why UDP also provides checking and verification. The reason is that the protocols below the link layer may not provide error detection in some channels between the source and the terminal. Although UDP provides error detection, when an error is detected, UDP does not perform error correction. It simply throws away the damaged message segment or provides warning information to the application.
3.main feature
UDP is a connectionless protocol. The source and terminal do not establish a connection before transmitting data. When it wants to transmit, it simply grabs the data from the application and throws it on the network as quickly as possible. On the sending end, the speed of UDP transmission of data is only limited by the speed at which the application generates data, the capacity of the computer, and the transmission bandwidth; on the receiving end, UDP puts each message segment in the queue, and the application removes it from the queue every time Read a message segment.
Since the data transmission does not establish a connection, there is no need to maintain the connection status, including the receiving and sending status, so a server can transmit the same message to multiple clients at the same time.
The header of the UDP packet is very short, only 8 bytes. Compared with the 20-byte packet of TCP, the extra overhead of UDP is very small. Throughput is not adjusted by the congestion control algorithm, but only limited by the data rate, transmission bandwidth, source and terminal host performance of the application software. UDP is message-oriented. The UDP of the sender delivers the message delivered by the application program down to the IP layer after the header is added. It neither splits nor merges, but preserves the boundaries of these messages. Therefore, the application needs to select the appropriate message size.
Although UDP is an unreliable protocol, it is an ideal protocol for distributing information. For example, reporting the stock market on the screen, displaying aviation information, and so on. UDP is also used in routing information protocol RIP (Routing Information Protocol) to modify the routing table. In these applications, if a message is lost, another new message will replace it after a few seconds. UDP is widely used in multimedia applications.
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How far(long) the transmitter cover?
The transmission range depends on many factors. The true distance is based on the antenna installing height , antenna gain, using environment like building and other obstructions , sensitivity of the receiver, antenna of the receiver . Installing antenna more high and using in the countryside , the distance will much more far.
EXAMPLE 5W FM Transmitter use in the city and hometown:
I have a USA customer use 5W fm transmitter with GP antenna in his hometown ,and he test it with a car, it cover 10km(6.21mile).
I test the 5W fm transmitter with GP antenna in my hometown ,it cover about 2km(1.24mile).
I test the 5W fm transmitter with GP antenna in Guangzhou city ,it cover about only 300meter(984ft).
Below are the approximate range of different power FM Transmitters. ( The range is diameter )
0.1W ~ 5W FM Transmitter ：100M ~1KM
5W ~15W FM Ttransmitter : 1KM ~ 3KM
15W ~ 80W FM Transmitter : 3KM ~10KM
80W ~500W FM Transmitter : 10KM ~30KM
500W ~1000W FM Transmitter : 30KM ~ 50KM
1KW ~ 2KW FM Transmitter : 50KM ~100KM
2KW ~5KW FM Transmitter : 100KM ~150KM
5KW ~10KW FM Transmitter : 150KM ~200KM
How to contact us for the transmitter?
Call me +8618078869184 OR
Email me [email protected]
1.How far you want to cover in diameter ?
2.How tall of you tower ?
3.Where are you from ?
And we will give you more professional advice.
About Us
FMUSER.ORG is a system integration company focusing on RF wireless transmission / studio video audio equipment / streaming and data processing .We are providing everything from advice and consultancy through rack integration to installation, commissioning and training.
We offer FM Transmitter, Analog TV Transmitter, Digital TV transmitter, VHF UHF Transmitter, Antennas, Coaxial Cable Connectors, STL, On Air Processing, Broadcast Products for the Studio, RF Signal Monitoring, RDS Encoders, Audio Processors and Remote Site Control Units, IPTV Products, Video / Audio Encoder / Decoder, designed to meet the needs of both large international broadcast networks and small private stations alike.
Our solution has FM Radio Station / Analog TV Station / Digital TV Station / Audio Video Studio Equipment / Studio Transmitter Link / Transmitter Telemetry System / Hotel TV System / IPTV Live Broadcasting / Streaming Live Broadcast / Video Conference / CATV Broadcasting system.
We are using advanced technology products for all the systems, because we know the high reliability and high performance are so important for the system and solution . At the same time we also have to make sure our products system with a very reasonable price.
We have customers of public and commercial broadcasters, telecom operators and regulation authorities , and we also offer solution and products to many hundreds of smaller, local and community broadcasters .
FMUSER.ORG has been exporting more than 15 years and have clients all over the world. With 13 years experience in this field ,we have a professional team to solve customer's all kinds of problems. We dedicated in supplying the extremely reasonable pricing of professional products & services. Contact email : [email protected]
Our Factory
We have modernization of the factory . You are welcome to visit our factory when you come to China.
At present , there are already 1095 customers around the world visited our Guangzhou Tianhe office . If you come to China , you are welcome to visit us .
At Fair
This is our participation in 2012 Global Sources Hong Kong Electronics Fair . Customers from all over the world finally have a chance to get together.
Where is Fmuser ?
You can search this numbers " 23.127460034623816,113.33224654197693 " in google map , then you can find our fmuser office .
FMUSER Guangzhou office is in Tianhe District which is the center of the Canton . Very near to the Canton Fair , guangzhou railway station, xiaobei road and dashatou , only need 10 minutes if take TAXI . Welcome friends around the world to visit and negotiate .
Contact: Sky Blue
Cellphone: +8618078869184
WhatsApp: +8618078869184
Wechat: +8618078869184
E-mail: [email protected]
QQ: 727926717
Skype: sky198710021
Address: No.305 Room HuiLan Building No.273 Huanpu Road Guangzhou China Zip:510620
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English: We accept all payments , such as PayPal, Credit Card, Western Union, Alipay, Money Bookers, T/T, LC, DP, DA, OA, Payoneer, If you have any question , please contact me [email protected] or WhatsApp +8618078869184
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But if you have not a credit card and not have a paypal account or difficult to got a paypal accout ,You can use the following:
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Pay by Western Union to me :
First name/Given name: Yingfeng
Last name/Surname/ Family name: Zhang
Full name: Yingfeng Zhang
Country: China
City: Guangzhou
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T/T . Pay by T/T (wire transfer/ Telegraphic Transfer/ Bank Transfer)
First BANK INFORMATION (COMPANY ACCOUNT):
SWIFT BIC: BKCHHKHHXXX
Bank name: BANK OF CHINA (HONG KONG) LIMITED, HONG KONG
Bank Address: BANK OF CHINA TOWER, 1 GARDEN ROAD, CENTRAL, HONG KONG
BANK CODE: 012
Account Name : FMUSER INTERNATIONAL GROUP LIMITED
Account NO. : 012-676-2-007855-0
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Second BANK INFORMATION (COMPANY ACCOUNT):
Beneficiary: Fmuser International Group Inc
Account Number: 44050158090900000337
Beneficiary's Bank: China Construction Bank Guangdong Branch
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Address: NO.553 Tianhe Road, Guangzhou, Guangdong,Tianhe District, China
**Note: When you transfer money to our bank account, please DO NOT write anything in the remark area, otherwise we won't be able to receive the payment due to government policy on international trade business.
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* It will be sent in 1-2 working days when payment clear.
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* If the packages is below 2kg,we will be shipped via post airmail, it will take about 15-25days to your hand.
If the package is more than 2kg,we will ship via EMS , DHL , UPS, Fedex fast express delivery,it will take about 7~15days to your hand.
If the package more than 100kg , we will send via DHL or air freight. It will take about 3~7days to your hand.
All the packages are form China guangzhou.
* Package will be sent as a "gift" and declear as less as possible,buyer don't need to pay for "TAX".
* After ship, we will send you an E-mail and give you the tracking number.
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For Warranty .
Contact US--->>Return the item to us--->>Receive and send another replace .
Name: Liu xiaoxia
Address: 305Fang HuiLanGe HuangPuDaDaoXi 273Hao TianHeQu Guangzhou China.
ZIP:510620
Phone: +8618078869184
Please return to this address and write your paypal address,name,problem on note: |
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