IOS Socket Programming

I. Network protocols: TCP/IP, sockets, HTTP, etc.
The network seven layer is from the bottom up to the physical layer, the data link layer, the network layer, the transport layer, the conversation layer, the presentation layer and the application layer respectively.
The physical layer, the data link layer and the network layer are often called media layers, which are the objects researched by network engineers.
The transport layer, the session layer, the presentation layer, and the application layer are referred to as the host layer and are the content that the user is looking for and cares about.
The HTTP protocol corresponds to the application layer
The TCP protocol corresponds to the transport layer
IP protocol corresponds to the network layer
The three are not comparable in nature. Moreover, the HTTP protocol is based on TCP connections.
TCP/IP is a Transport layer protocol that mainly addresses how data travels across the network, while HTTP is an application-layer protocol that addresses how data is packaged.
When we transmit data, we can use only the transport layer (TCP/IP), but in that case, because there is no application layer, the data content is not recognized, if you want to make the transferred data meaningful, you must use the Application layer protocol, the application layer protocol, there are HTTP, FTP, Telnet and so on, You can also define the application layer protocol yourself. The web uses HTTP as the Transport Layer protocol to encapsulate HTTP text information and then send it to the network using TCP/IP as the Transport layer protocol. Socket is the TCP/IP protocol encapsulation, the socket itself is not a protocol, but a call interface (API), through the socket, we can use the TCP/IP protocol.
Two, HTTP and socket connection differences
I believe many of the novice mobile phone networking development friends want to know what is the difference between the HTTP and socket connection, hope that through their own shallow understanding can help beginners.
2.1. TCP connection
To understand the socket connection, you need to understand the TCP connection first. Mobile phone can use the network function is because the bottom of the mobile phone implementation of TCP/IP protocol, you can make the mobile phone terminal through the wireless network to establish a TCP connection. TCP protocol can provide an interface to the upper network, so that the transmission of the upper network data is based on the "No Difference" network.
Setting up a TCP connection requires a "three-time handshake":
First handshake: The client sends a SYN packet (SYN=J) to the server and enters the Syn_send state, waiting for the server to confirm;
Second handshake: The server receives the SYN packet, it must confirm the customer's SYN (ACK=J+1), and also send itself a SYN packet (syn=k), that is, the Syn+ack packet, when the server enters the SYN_RECV state;
Third handshake: The client receives the server's Syn+ack packet, sends the acknowledgment packet ack (ACK=K+1) to the server, the packet is sent, the client and the server enter the established state, and the handshake is completed three times.
The data is not included in the packets that are delivered during the handshake, and the client and server formally begin transmitting the data after the three handshake is complete. Ideally, once a TCP connection is established, the TCP connection is maintained until either side of the communication actively closes the connection. When disconnected, both the server and the client can initiate a request to disconnect the TCP connection, and the disconnection process requires a "four handshake" (the process is not fine-grained, that is, the server interacts with the client and finally determines the disconnection)
2.2. HTTP connection
The HTTP protocol, the Hypertext Transfer Protocol (Hypertexttransfer Protocol), is the foundation of Web networking and one of the most commonly used protocols for mobile networking, an application built on the TCP protocol.
The most notable feature of an HTTP connection is that each request sent by the client requires a server loopback response, and the connection is actively released after the request has ended. The process from establishing a connection to closing a connection is called a "one-time connection."
1) in HTTP 1.0, each request from the client requires a separate connection to be established, and the connection is automatically freed after the request is processed.
2) in HTTP 1.1, multiple requests can be processed in a single connection, and multiple requests can overlap, without waiting for a request to end before sending the next request.
Because HTTP is actively releasing the connection after each request ends, the HTTP connection is a "short connection", which requires constant connection requests to the server to maintain the client program's online status. As a general practice, there is no need to obtain any data immediately, and the client will keep a "keep-connected" request to the server at regular intervals, and the server responds to the client after receiving the request, indicating that the client is "online". If the server can not receive the client's request for a long time, it is considered that the client "offline", if the client cannot receive a reply from the server for a long time, it is considered that the network has been disconnected.
Three, Socket principle
3.1. Socket (socket) concept
Socket (socket) is the cornerstone of communication and is the basic operating unit of network communication supporting TCP/IP protocol. It is an abstract representation of the endpoint in the network communication process and contains five kinds of information that must be used for network communication: the protocol that the connection uses, the IP address of the local host, the protocol port of the local process, the IP address of the remote host, and the protocol port of the remote process.
When the application layer communicates data through the transport layer, TCP encounters a problem that provides concurrent services for multiple application processes at the same time. Multiple TCP connections or multiple application processes may require data to be transmitted over the same TCP protocol port. To differentiate between different application processes and connections, many computer operating systems provide a socket (socket) interface for applications interacting with the TCP/IP protocol. The application layer can communicate with the transport layer through the socket interface, differentiate the communication from different application processes or network connections, and realize the concurrent service of data transmission.
3.2. Establish socket connection
Establishing a socket connection requires at least one pair of sockets, one running on the client, called Clientsocket, and the other running on the server side, called ServerSocket.
The connection between sockets is divided into three steps: Server listening, client request, connection acknowledgement.
Server monitoring: Server-side sockets do not locate specific client sockets, but are waiting for the status of the connection, real-time monitoring network status, waiting for the client connection request.
Client request: Refers to the client's socket to make a connection request, to connect to the target is the server-side socket. To do this, the client's socket must first describe the socket of the server it is connecting to, indicate the address and port number of the server-side socket, and then make a connection request to the server-side socket.
Connection confirmation: When a server-side socket hears or receives a connection request from a client socket, it responds to a client socket request, establishes a new thread, sends a description of the server-side socket to the client, and once the client confirms the description, the two sides formally establish the connection. While the server-side socket continues to be in the listening state, it continues to receive connection requests from other client sockets.
3.3. Socket connection and TCP connection
When you create a socket connection, you can specify the transport layer protocol used, which can support different transport layer protocols (TCP or UDP), which is a TCP connection when a connection is made using the TCP protocol.
3.4. Socket connection and HTTP connection
Since the socket connection is usually a TCP connection, once the socket connection is established, the communication parties can start sending data content to each other until the two sides are disconnected. However, in real network applications, the client-to-server communication often needs to traverse multiple intermediary nodes, such as routers, gateways, firewalls, and so on, most firewalls will turn off long inactive connections and cause the Socket connection to be disconnected, so it needs to be polled to tell the network that the connection is active.
The HTTP connection uses a "request-response" approach, not only to establish a connection at the time of the request, but also to be able to reply to the server after the client has made a request to the server.
In many cases, the server side is required to proactively push data to the client, keeping the client and server data in real time and in sync. At this point, if the two sides established a socket connection, the server can directly transfer the data to the client, if the two sides establish an HTTP connection, the server needs to wait until the client sends a request before the data can be sent back to the client, so the client periodically sends a connection request to the server, not only to remain online, It also asks the server if there is any new data, and if so, it passes the data to the client.
Here we use the socket to implement a chat room function, about the server here is not introduced.
One: the first input stream and the output stream and a message array in the header file

 @interface viewcontroller () <nsstreamdelegate,uitextfielddelegate, Uitableviewdatasource,uitableviewdelegate>{Nsinputstream *_inputstream;//corresponding input streamNsoutputstream *_outputstream;//corresponding output stream}@property(Weak,nonatomic)IboutletNslayoutconstraint *inputviewconstraint;@property(Weak,nonatomic)Iboutlet UITableView*tableview;@property(nonatomic,Strong)Nsmutablearray*CHATMSGS;//Chat message array@end

Lazy loading this message array

-(NSMutableArray *)chatMsgs{if (!_chatMsgs) {   _chatMsgs = [NSMutableArrayreturn _chatMsgs;}

Second: to realize the input and output stream monitoring

-(voidStream: (Nsstream *) Astream handleevent: (nsstreamevent) eventcode{NSLog(@"%@",[NsthreadCurrentThread]);//nsstreameventopencompleted = 1UL << 0,//input/output stream open complete//nsstreameventhasbytesavailable = 1UL << 1,//byte readable//nsstreameventhasspaceavailable = 1UL << 2,//can issue bytes//nsstreameventerroroccurred = 1UL << 3,//connection error occurred//nsstreameventendencountered = 1UL << 4//end of connection    Switch(EventCode) { CaseNsstreameventopencompleted:NSLog(@"Input output stream open complete"); Break; CaseNsstreameventhasbytesavailable:NSLog(@"byte-readable"); [ SelfReadData]; Break; CaseNsstreameventhasspaceavailable:NSLog(@"can send bytes"); Break; CaseNsstreameventerroroccurred:NSLog(@"Connection error occurred"); Break; CaseNsstreameventendencountered:NSLog(@"End of Connection");//Close the input/output stream[_inputstream Close]; [_outputstream Close];//Remove from main run cycle[_inputstream Removefromrunloop:[nsrunloop Mainrunloop] formode:nsdefaultrunloopmode]; [_outputstream Removefromrunloop:[nsrunloop Mainrunloop] formode:nsdefaultrunloopmode]; Break;default: Break; }}

Three: Linked server

- (ibaction) Connecttohost: (ID) Sender {//1. Establishing a connection  NSString*host = @"127.0.0.1";intPort =12345;//define C language input/output streamCfreadstreamref Readstream;   Cfwritestreamref Writestream; Cfstreamcreatepairwithsockettohost (NULL, (__bridge cfstringref) host, Port, &readstream, &writestream);//convert c input and output stream to OC object_inputstream = (__bridge Nsinputstream *) (Readstream); _outputstream = (__bridge Nsoutputstream *) (Writestream);//Set up proxy_inputstream. Delegate= Self; _outputstream. Delegate= Self;//Add input input stream to main run loop     //Do not add main run loop agent may not work[_inputstream Scheduleinrunloop:[nsrunloop Mainrunloop] formode:nsdefaultrunloopmode]; [_outputstream Scheduleinrunloop:[nsrunloop Mainrunloop] formode:nsdefaultrunloopmode];//Open input/output stream[_inputstream Open]; [_outputstream Open]; }

Four: Login

-(ibaction) Loginbtnclick: (ID) Sender {//Login    //Send user name and password    //When doing this, only the user name, password will not be sent    //If you want to log in, send the data format as "Iam:zhangsan";    //If you want to send a chat message, the data format is "Msg:did you have dinner";    //Sign-in instructionsNSString*Loginstr=@"Iam:zhangsan";//Turn str into NSDataNSData*Data = [Loginstr datausingencoding:nsutf8stringencoding]; [_outputstream write:Data.bytesMaxLength:Data.Length]; }

Five: Read server data

#pragma mark 读了服务器返回的数据 -(void)readData{    //建立一个缓冲区 可以放1024个字节    uint8_t buf[1024];    // 返回实际装的字节数     NSInteger len = [_inputStream read:buf maxLength:sizeof(buf)];    // 把字节数组转化成字符串     NSData *data = [NSData dataWithBytes:buf length:len];     // 从服务器接收到的数据     NSString *recStr =  [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];    NSLog(@"%@",recStr);     [self reloadDataWithText:recStr]; }

Six: Send data

-(BOOL) Textfieldshouldreturn: (Uitextfield *) textfield{NSString*text = TextField. Text;NSLog(@"%@", text);//Chat information    NSString*MSGSTR = [NSStringstringwithformat:@"msg:%@", text];//Turn str into NSDataNSData *data = [MsgStr datausingencoding:nsutf8stringencoding];//Refresh table[ SelfRELOADDATAWITHTEXT:MSGSTR];//Send data[_outputstream Write:data. BytesMaxlength:data. Length];//Send out data, empty TextFieldTextField. Text=Nil;return YES;}

Seven: Realize the display of data, and every message sent will scroll to the corresponding location

-(void) Reloaddatawithtext: (NSString*) text{[ Self. ChatmsgsAddobject:text]; [ Self. TableViewReloaddata];//Data many, should scroll upwards    Nsindexpath*lastpath = [NsindexpathIndexpathforrow: Self. Chatmsgs. Count-1Insection:0]; [ Self. TableViewScrolltorowatindexpath:lastpath Atscrollposition:uitableviewscrollpositionbottom Animated:YES]; }#pragma the data source for the Mark table-(Nsinteger) TableView: (UITableView*) TableView numberofrowsinsection: (Nsinteger) section{return  Self. Chatmsgs. Count; } - (UITableViewCell*) TableView: (UITableView*) TableView Cellforrowatindexpath: (Nsindexpath*) Indexpath {Static NSString*id = @"Cell";UITableViewCell*cell = [TableView dequeuereusablecellwithidentifier:id]; Cell. Textlabel. Text= Self. Chatmsgs[Indexpath. Row];returnCell } -(void) Scrollviewwillbegindragging: (Uiscrollview*) scrollview{[ Self. ViewEndediting:YES]; }

Eight: Monitor keyboard changes

  //Monitor keyboard[[NsnotificationcenterDefaultcenter] Addobserver: SelfSelector@selector(Kbfrmwillchange:) Name:uikeyboardwillchangeframenotification object:Nil]; }-(void) Kbfrmwillchange: (nsnotification*) noti{NSLog(@"%@", Noti. UserInfo);//Gets the height of the window    CGFloatWINDOWH = [UIScreen mainscreen]. Bounds. Size. Height;//keyboard end of frm    CGRectKBENDFRM = [Noti. UserInfo[Uikeyboardframeenduserinfokey] Cgrectvalue];//Get the Y value of the keyboard end    CGFloatKbendy = kbendfrm. Origin. Y; Self. Inputviewconstraint. Constant= Windowh-kbendy; }

IOS Socket Programming