NDK学习笔记(十) POSIX Sockect 面向无连接的通信

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下面只是代码片段，想看详细的代码请clone代码。
本人没有在android虚拟机上看到通信成功，试了好多配置依然不行，过段时间找两个手机再试试。
运行项目时，如果要看tcp的，则需要更改ClientTask、ServerTask类中的onBackground方法，将jni方法替换成tcp的。udp的也一样，udp的则替换成udp的jni方法。

地址：https://gitee.com/xd_box/NDK_Socket

1.接收数据报

__fd：socket实例
__buf：保存从socket接收的数据
__n：缓冲区大小
__flags：额外标志
__src_addr：保存客户端发送包的协议地址
__src_addr_length：协议地址的内存空间大小成功返回接收到的字节数，失败返回-1
__socketcall ssize_t recvfrom(int __fd, void* __buf, size_t __n, int __flags, struct sockaddr* __src_addr, socklen_t* __src_addr_length);

static ssize_t ReceiveDatagramFromSocket(JNIEnv *env, jobject obj, int sd,struct sockaddr_in *address, char *buffer,size_t bufferSize) {socklen_t addressLength = sizeof(struct sockaddr_in);//从socket中接受数据包LogMessage(env, obj, "从socket接受数据");ssize_t recvSize = recvfrom(sd, buffer, bufferSize, 0, (struct sockaddr *) address,&addressLength);if (-1 == recvSize) {ThrowErrnoException(env, "java/io/IOException", errno);} else {LogAddress(env, obj, "接收到", address);//以NULL种植缓冲区使其为一个字符串buffer[recvSize] = NULL;if (recvSize > 0) {LogMessage(env, obj, "接收到%d字节：%s", recvSize, buffer);}}return recvSize;
}

2.发送数据报

__fd：socket实例
__buf：要发送的数据的指针
__n：缓冲区大小
__flags：额外标志
__dst_addr：目标地址
__dst_addr_length：地址结构大小成功返回传送的字节数，失败但会-1
__socketcall ssize_t sendto(int __fd, const void* __buf, size_t __n, int __flags, const struct sockaddr* __dst_addr, socklen_t __dst_addr_length);

static ssize_t SendDatagramToSpcket(JNIEnv *env, jobject obj, int sd,const struct sockaddr_in *address, const char *buffer,size_t bufferSize) {LogAddress(env, obj, "Sending to", address);ssize_t sentSize = sendto(sd, buffer, bufferSize, 0, (const sockaddr *) address,sizeof(struct sockaddr_in));if (-1 == sentSize) {ThrowErrnoException(env, "java/io/IOException", errno);} else if (sentSize > 0) {LogMessage(env, obj, "sent %d 字节：%s", sentSize, buffer);}return sentSize;
}

3.udp服务

开启udp服务

extern "C"
JNIEXPORT void JNICALL
Java_com_example_testnt_EchoServerActivity_nativeStartUdpServer(JNIEnv *env, jobject thiz,jint port) {int serverSocket = NewUdpSocket(env, thiz);if (NULL == env->ExceptionOccurred()) {BindSocketToPort(env, thiz, serverSocket, (unsigned short) port);if (NULL != env->ExceptionOccurred()) {goto exit;}if (0 == port) {GetSocketPort(env, thiz, serverSocket);if (NULL != env->ExceptionOccurred()) {goto exit;}}struct sockaddr_in address;memset(&address, 0, sizeof(address));char buffer[MAX_BUFFER_SZIE];ssize_t recvSize;ssize_t sentSize;//接收recvSize = ReceiveDatagramFromSocket(env, thiz, serverSocket, &address, buffer,MAX_BUFFER_SZIE);if ((0 == recvSize) || (NULL != env->ExceptionOccurred())) {goto exit;}sentSize = SendDatagramToSpcket(env, thiz, serverSocket, &address, buffer,(size_t) recvSize);if ((0 == sentSize) || (NULL != env->ExceptionOccurred())) {goto exit;}}exit:if (serverSocket > 0) {close(serverSocket);}
}

4.udp客户端

extern "C"
JNIEXPORT void JNICALL
Java_com_example_testnt_EchoClientActivity_nativeStartUdpClient(JNIEnv *env, jobject thiz,jstring ip, jint port,jstring message) {int clientSocket = NewUdpSocket(env, thiz);if (NULL == env->ExceptionOccurred()) {struct sockaddr_in address;memset(&address, 0, sizeof(address));address.sin_family = PF_INET;const char *ipAddress = env->GetStringUTFChars(ip, NULL);if (NULL == ipAddress) {goto exit;}//将IP地址字符串转换为网络地址int result = inet_aton(ipAddress, &(address.sin_addr));env->ReleaseStringUTFChars(ip, ipAddress);if (0 == result) {ThrowErrnoException(env, "java/io/IOException", errno);goto exit;}//转换为网络字节顺序address.sin_port = htons(port);const char *messageText = env->GetStringUTFChars(message, NULL);if (NULL == messageText) {goto exit;}jsize messageSize = env->GetStringUTFLength(message);//发送SendDatagramToSpcket(env, thiz, clientSocket, &address, messageText, (size_t) messageSize);env->ReleaseStringUTFChars(message, messageText);//失败if (NULL != env->ExceptionOccurred()) {goto exit;}char buffer[MAX_BUFFER_SZIE];memset(&address, 0, sizeof(address));ReceiveDatagramFromSocket(env, thiz, clientSocket, &address, buffer, MAX_BUFFER_SZIE);}exit:if (clientSocket > 0) {close(clientSocket);}
}

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