iOS Socket UDP编程-C语言版

1. UDP Socket编程

先讲一讲

UDP

编程，因为比

TCP

要简单多了。首先，我们需要明白

UDP

是用户数据报协议，英文名为User
Datagram Protocol，它是面向无连接的。

注意：

Socket

通信一定有要服务端和客户端。

1.1 UDP Socket客户端

客户端的工作流程：首先调用

socket

函数创建一个

Socket

，然后指定服务端的

IP

地址和端口号，就可以调用

sendto

将字符串传送给服务器端，并可以调用

recvfrom

接收服务器端返回的字符串，最后关闭该socket。

笔者这里分成了四步：

第一步：创建

socket

并配置

socket

，如服务端

ip

地址和端口号

第二步：调用

sendto

发送消息到服务器端

第三步：调用

recvfrom

接收来自服务器端的消息

第四步：调用

close

关闭

socket

1.1.1 客户端的代码实现：

- (void)udpClient {
int clientSocketId;
ssize_t len;
socklen_t addrlen;
struct sockaddr_in client_sockaddr;
char buffer[256] = "Hello, server, how are you?";

// 第一步：创建Socket
clientSocketId = socket(AF_INET, SOCK_DGRAM, 0);
if(clientSocketId < 0) {
NSLog(@"creat client socket fail\n");
return;
}

addrlen = sizeof(struct sockaddr_in);
bzero(&client_sockaddr, addrlen);
client_sockaddr.sin_family = AF_INET;
client_sockaddr.sin_addr.s_addr = inet_addr("192.168.1.107");
client_sockaddr.sin_port = htons(1024);

int count = 10;
do {
bzero(buffer, sizeof(buffer));
sprintf(buffer, "%s", "Hello, server, how are you?");

// 第二步：发送消息到服务端
// 注意:UDP是面向无连接的，因此不用调用connect()
// 将字符串传送给server端
len = sendto(clientSocketId, buffer, sizeof(buffer), 0, (struct sockaddr *)&client_sockaddr, addrlen);

if (len > 0) {
NSLog(@"发送成功");
} else {
NSLog(@"发送失败");
}

// 第三步：接收来自服务端返回的消息
// 接收server端返回的字符串
bzero(buffer, sizeof(buffer));
len = recvfrom(clientSocketId, buffer, sizeof(buffer), 0, (struct sockaddr *)&client_sockaddr, &addrlen);
NSLog(@"receive message from server: %s", buffer);

count--;
} while (count >= 0);

// 第四步：关闭socket
// 由于是面向无连接的，消息发出处就可以了，不用管它收不收得到，发完就可以关闭了
close(clientSocketId);
}

1.1.2 客户端的打印日志

2015-12-06 15:38:36.095 iOS-Socket-C-Version-Client[9709:4234848] 发送成功
2015-12-06 15:38:36.286 iOS-Socket-C-Version-Client[9709:4234848] receive message from server: Hello, server, how are you?
2015-12-06 15:38:36.286 iOS-Socket-C-Version-Client[9709:4234848] 发送成功
2015-12-06 15:38:36.291 iOS-Socket-C-Version-Client[9709:4234848] receive message from server: Hello, server, how are you?
2015-12-06 15:38:36.291 iOS-Socket-C-Version-Client[9709:4234848] 发送成功
2015-12-06 15:38:36.296 iOS-Socket-C-Version-Client[9709:4234848] receive message from server: Hello, server, how are you?
2015-12-06 15:38:36.296 iOS-Socket-C-Version-Client[9709:4234848] 发送成功
2015-12-06 15:38:36.316 iOS-Socket-C-Version-Client[9709:4234848] receive message from server: Hello, server, how are you?
2015-12-06 15:38:36.317 iOS-Socket-C-Version-Client[9709:4234848] 发送成功
2015-12-06 15:38:36.324 iOS-Socket-C-Version-Client[9709:4234848] receive message from server: Hello, server, how are you?
2015-12-06 15:38:36.324 iOS-Socket-C-Version-Client[9709:4234848] 发送成功
2015-12-06 15:38:36.328 iOS-Socket-C-Version-Client[9709:4234848] receive message from server: Hello, server, how are you?
2015-12-06 15:38:36.329 iOS-Socket-C-Version-Client[9709:4234848] 发送成功
2015-12-06 15:38:36.339 iOS-Socket-C-Version-Client[9709:4234848] receive message from server: Hello, server, how are you?
2015-12-06 15:38:36.339 iOS-Socket-C-Version-Client[9709:4234848] 发送成功
2015-12-06 15:38:36.355 iOS-Socket-C-Version-Client[9709:4234848] receive message from server: Hello, server, how are you?
2015-12-06 15:38:36.356 iOS-Socket-C-Version-Client[9709:4234848] 发送成功
2015-12-06 15:38:36.366 iOS-Socket-C-Version-Client[9709:4234848] receive message from server: Hello, server, how are you?
2015-12-06 15:38:36.366 iOS-Socket-C-Version-Client[9709:4234848] 发送成功
2015-12-06 15:38:36.372 iOS-Socket-C-Version-Client[9709:4234848] receive message from server: Hello, server, how are you?
2015-12-06 15:38:36.373 iOS-Socket-C-Version-Client[9709:4234848] 发送成功
2015-12-06 15:38:36.392 iOS-Socket-C-Version-Client[9709:4234848] receive message from server: Hello, server, how are you?

1.2 UDP Socket服务器端

服务器端的工作流程：首先调用

socket

函数创建一个套接字，然后调用

bind

函数将其与本机地址以及一个本地端口号绑定，接收到一个客户端时，服务器显示该客户端的IP地址，并将字串返回给客户端。

笔者这里分成了五步：

第一步：创建

socket

并配置

socket

第二步：调用

bind

绑定服务器本机ip及端口号

第三步：调用

recvfrom

接收来自客户端的消息

第四步：调用

sendto

将接收到服务器端的信息返回给客户端

第四步：调用

close

关闭

socket

1.2.1 服务器端代码实现

- (void)udpServer {
int serverSockerId = -1;
ssize_t len = -1;
socklen_t addrlen;
char buff[1024];
struct sockaddr_in ser_addr;

// 第一步：创建socket
// 注意，第二个参数是SOCK_DGRAM，因为udp是数据报格式的
serverSockerId = socket(AF_INET, SOCK_DGRAM, 0);

if(serverSockerId < 0) {
NSLog(@"Create server socket fail");
return;
}

addrlen = sizeof(struct sockaddr_in);
bzero(&ser_addr, addrlen);

ser_addr.sin_family = AF_INET;
ser_addr.sin_addr.s_addr = htonl(INADDR_ANY);
ser_addr.sin_port = htons(1024);

// 第二步：绑定端口号
if(bind(serverSockerId, (struct sockaddr *)&ser_addr, addrlen) < 0) {
NSLog(@"server connect socket fail");
return;
}

do {
bzero(buff, sizeof(buff));

// 第三步：接收客户端的消息
len = recvfrom(serverSockerId, buff, sizeof(buff), 0, (struct sockaddr *)&ser_addr, &addrlen);
// 显示client端的网络地址
NSLog(@"receive from %s\n", inet_ntoa(ser_addr.sin_addr));
// 显示客户端发来的字符串
NSLog(@"recevce:%s", buff);

// 第四步：将接收到的客户端发来的消息，发回客户端
// 将字串返回给client端
sendto(serverSockerId, buff, len, 0, (struct sockaddr *)&ser_addr, addrlen);
} while (strcmp(buff, "exit") != 0);

// 第五步：关闭socket
close(serverSockerId);
}

1.2.2 服务器端的打印日志

2015-12-06 15:38:36.268 iOS-Socket-C-Version-Server[39130:2473780] receive from 192.168.1.100
2015-12-06 15:38:36.269 iOS-Socket-C-Version-Server[39130:2473780] recevce:Hello, server, how are you?
2015-12-06 15:38:36.372 iOS-Socket-C-Version-Server[39130:2473780] receive from 192.168.1.100
2015-12-06 15:38:36.372 iOS-Socket-C-Version-Server[39130:2473780] recevce:Hello, server, how are you?
2015-12-06 15:38:36.377 iOS-Socket-C-Version-Server[39130:2473780] receive from 192.168.1.100
2015-12-06 15:38:36.377 iOS-Socket-C-Version-Server[39130:2473780] recevce:Hello, server, how are you?
2015-12-06 15:38:36.382 iOS-Socket-C-Version-Server[39130:2473780] receive from 192.168.1.100
2015-12-06 15:38:36.382 iOS-Socket-C-Version-Server[39130:2473780] recevce:Hello, server, how are you?
2015-12-06 15:38:36.405 iOS-Socket-C-Version-Server[39130:2473780] receive from 192.168.1.100
2015-12-06 15:38:36.405 iOS-Socket-C-Version-Server[39130:2473780] recevce:Hello, server, how are you?
2015-12-06 15:38:36.409 iOS-Socket-C-Version-Server[39130:2473780] receive from 192.168.1.100
2015-12-06 15:38:36.410 iOS-Socket-C-Version-Server[39130:2473780] recevce:Hello, server, how are you?
2015-12-06 15:38:36.414 iOS-Socket-C-Version-Server[39130:2473780] receive from 192.168.1.100
2015-12-06 15:38:36.415 iOS-Socket-C-Version-Server[39130:2473780] recevce:Hello, server, how are you?
2015-12-06 15:38:36.425 iOS-Socket-C-Version-Server[39130:2473780] receive from 192.168.1.100
2015-12-06 15:38:36.426 iOS-Socket-C-Version-Server[39130:2473780] recevce:Hello, server, how are you?
2015-12-06 15:38:36.441 iOS-Socket-C-Version-Server[39130:2473780] receive from 192.168.1.100
2015-12-06 15:38:36.441 iOS-Socket-C-Version-Server[39130:2473780] recevce:Hello, server, how are you?
2015-12-06 15:38:36.452 iOS-Socket-C-Version-Server[39130:2473780] receive from 192.168.1.100
2015-12-06 15:38:36.452 iOS-Socket-C-Version-Server[39130:2473780] recevce:Hello, server, how are you?
2015-12-06 15:38:36.472 iOS-Socket-C-Version-Server[39130:2473780] receive from 192.168.1.100
2015-12-06 15:38:36.473 iOS-Socket-C-Version-Server[39130:2473780] recevce:Hello, server, how are you?

我们这里打印出了客户端发来的消息，由于上面实现的代码中，只发10次，所以这里只有10条。

源代码

小伙伴们，可以到github下载了：https://github.com/CoderJackyHuang/iOS-Socket-C-Version

注意：这里面有两个工程，一个是客户端，一个是服务器端。运行时，先运行服务器端，然后再选择客户端。另外，客户端所指定的服务器端的ip地址一定要修改成您本机对应的ip，不然使用笔者这里的ip就会失败。